C programming is a general-purpose language developed in the 1970s to write operating systems like UNIX. It is one of the most widely used languages, particularly for systems programming. Some key facts: C was created to develop UNIX and is still widely used for operating systems, compilers, databases and other modern programs. It has various data types like integers, floats, characters, arrays and structures. Variables are defined with a data type and can be initialized. C code is written in files with a .c extension and preprocessed before compilation.
This document discusses different types of functions in C programming. It defines library functions, user-defined functions, and the key elements of functions like prototypes, arguments, parameters, return values. It categorizes functions based on whether they have arguments and return values. The document also explains how functions are called, either by value where changes are not reflected back or by reference where the original values are changed.
The document discusses storage classes in C programming which determine where a variable is stored in memory and the scope and lifetime of a variable. There are four main storage classes - automatic, external, static and register. Automatic variables are local to a block and vanish after the block ends. External variables can be accessed from other files. Static variables retain their value between function calls and last the lifetime of the program. Register variables are stored in CPU registers for faster access but there are limited registers.
C and C++ are programming languages with many similarities but some key differences. They both use basic built-in data types and control structures. However, C++ supports object-oriented programming features like classes, data hiding, and inheritance that are not present in C. C++ also supports function overloading, namespaces, and references, which provide more flexibility than C at the cost of additional complexity. Overall, C++ can be seen as an enhancement of C with additional high-level programming capabilities.
C was developed in the early 1970s by Dennis Ritchie at Bell Labs as an evolution of ALGOL, BCPL, and B programming languages. It became widely popular after the publication of "The C Programming Language" book in 1978. C was later standardized as ANSI C in 1989 and ISO/IEC 9899 in 1990. The language continued to evolve with extensions and refinements such as C99. C remains one of the most widely used programming languages due to its portability and role in developing operating systems like UNIX.
An array is a collection of data that holds a fixed number of values of the same type. Arrays allow storing multiple values in a single variable through indices. There are one-dimensional, two-dimensional, and multi-dimensional arrays. One-dimensional arrays use a single subscript, two-dimensional arrays use two subscripts like rows and columns, and multi-dimensional arrays can have more than two subscripts. Arrays can be initialized during declaration with values or initialized at runtime by user input or other methods. Elements are accessed using their indices and operations can be performed on the elements.
The document provides an overview of the C++ programming language. It discusses the history and development of C++, with key points being that C++ was created by Bjarne Stroustrup in 1983 as an extension of C to support object-oriented programming. It then covers some of the main differences between C and C++, uses of C++, advantages and disadvantages, standard libraries, basic C++ structures like data types, variables, operators, functions, arrays, and pointers.
This document discusses variables in C programming. It explains that variables are names that refer to memory locations where values can be stored and changed during program execution. It provides the syntax for declaring variables using different data types like int, float, double, and char. Rules for variable names are also outlined, such as starting with a letter or underscore and avoiding reserved words.
Introduction to control structure in C Programming Language include decision making (if statement, if..else statement, if...else if...else statement, nested if...else statement, switch...case statement), Loop(for loop, while loop, do while loop, nested loop) and using keyword(break, continue and goto)
This document discusses different types of functions in C programming. It defines library functions, user-defined functions, and the key elements of functions like prototypes, arguments, parameters, return values. It categorizes functions based on whether they have arguments and return values. The document also explains how functions are called, either by value where changes are not reflected back or by reference where the original values are changed.
The document discusses storage classes in C programming which determine where a variable is stored in memory and the scope and lifetime of a variable. There are four main storage classes - automatic, external, static and register. Automatic variables are local to a block and vanish after the block ends. External variables can be accessed from other files. Static variables retain their value between function calls and last the lifetime of the program. Register variables are stored in CPU registers for faster access but there are limited registers.
C and C++ are programming languages with many similarities but some key differences. They both use basic built-in data types and control structures. However, C++ supports object-oriented programming features like classes, data hiding, and inheritance that are not present in C. C++ also supports function overloading, namespaces, and references, which provide more flexibility than C at the cost of additional complexity. Overall, C++ can be seen as an enhancement of C with additional high-level programming capabilities.
C was developed in the early 1970s by Dennis Ritchie at Bell Labs as an evolution of ALGOL, BCPL, and B programming languages. It became widely popular after the publication of "The C Programming Language" book in 1978. C was later standardized as ANSI C in 1989 and ISO/IEC 9899 in 1990. The language continued to evolve with extensions and refinements such as C99. C remains one of the most widely used programming languages due to its portability and role in developing operating systems like UNIX.
An array is a collection of data that holds a fixed number of values of the same type. Arrays allow storing multiple values in a single variable through indices. There are one-dimensional, two-dimensional, and multi-dimensional arrays. One-dimensional arrays use a single subscript, two-dimensional arrays use two subscripts like rows and columns, and multi-dimensional arrays can have more than two subscripts. Arrays can be initialized during declaration with values or initialized at runtime by user input or other methods. Elements are accessed using their indices and operations can be performed on the elements.
The document provides an overview of the C++ programming language. It discusses the history and development of C++, with key points being that C++ was created by Bjarne Stroustrup in 1983 as an extension of C to support object-oriented programming. It then covers some of the main differences between C and C++, uses of C++, advantages and disadvantages, standard libraries, basic C++ structures like data types, variables, operators, functions, arrays, and pointers.
This document discusses variables in C programming. It explains that variables are names that refer to memory locations where values can be stored and changed during program execution. It provides the syntax for declaring variables using different data types like int, float, double, and char. Rules for variable names are also outlined, such as starting with a letter or underscore and avoiding reserved words.
Introduction to control structure in C Programming Language include decision making (if statement, if..else statement, if...else if...else statement, nested if...else statement, switch...case statement), Loop(for loop, while loop, do while loop, nested loop) and using keyword(break, continue and goto)
- Bitwise operators operate on individual bits of integer values and perform operations like AND, OR, XOR, and NOT.
- Negative integers are stored in two's complement form.
- Bitwise operators include & for AND, | for OR, ^ for XOR, ~ for NOT, << for left shift, >> for right shift, and >>> for unsigned right shift.
This document provides an overview of the C programming language. It begins with an outline of topics covered, then defines C as a structured, high-level, machine-independent language that follows a top-down approach. The document traces the history and evolution of C from earlier languages like ALGOL and BCPL. It describes key features of C like portability, speed, and simplicity. It also explains the roles of compilers and linkers and includes flowcharts, sample programs, and discussions of variables, data types, operators, and control statements in C like if/else statements and switch cases.
The document discusses the character set, keywords, and identifiers in the C programming language. It provides lists of uppercase and lowercase letters, digits, and special characters that are valid in C. It also lists and describes common keywords for data types, qualifiers, loop controls, user-defined types, jumping controls, and storage classes. Rules for writing identifiers are outlined, noting they must start with a letter, can include letters, digits, and underscores, and the first 31 characters are significant to the compiler.
Presentation on C++ Programming Languagesatvirsandhu9
This document provides an overview of the C++ programming language. It discusses why C++ is used, how it compares to Fortran, and the basic structure and components of a C++ program. The key topics covered include data types, variables, operators, selection statements, iteration statements, functions, arrays, pointers, input/output, preprocessor instructions, and comments. The document is intended to teach the basics of C++ programming in a structured way over multiple sections.
C++ is an object-oriented programming language that is an extension of C. It was developed in the 1980s to support object-oriented programming. In C++, data and functions can be combined into objects. Data in an object can only be accessed by the object's functions, allowing for encapsulation. The document then provides an overview of key C++ concepts like data types, tokens, operators, and input/output streams to introduce basic C++ syntax and programming.
This document discusses pointers in C++. It begins by defining pointers as variables that hold the memory addresses of other variables and explaining that pointers have types corresponding to the types of variables they point to. It then covers initializing and dereferencing pointers, constant pointers, pointer arithmetic, pointers and arrays, using pointers as function arguments, and memory management using pointers with the new and delete operators.
- An array is a collection of consecutive memory locations that all have the same name and type. An array allows storing multiple values of the same type using a single name.
- Arrays in C++ must be declared before use, specifying the type, name, and number of elements. Elements are accessed using an index.
- The main advantages of arrays are that they allow storing and processing large numbers of values efficiently using a single name. Arrays also make sorting and searching values easier.
This document provides an introduction to C++ programming. It discusses key differences between C and C++, shows simple C++ examples, and covers important C++ concepts like input/output streams, header files, inline functions, references, and reference parameters. The document is intended to teach basic C++ syntax and features to someone new to the language.
C Programming Language is the most popular computer language and most used programming language till now. It is very simple and elegant language. This lecture series will give you basic concepts of structured programming language with C.
The document discusses various data types in C++. It explains that data types define the type of data stored in variables and associated operations. There are fundamental data types like integer, character, float, double, and void provided by C++. User-defined data types include arrays, pointers, references, structures, unions, classes and enumerations. The document provides details on the size and range of standard data types like short int, int, long, float, double etc. It also explains various type modifiers and derived data types.
Increment and Decrement operators in C++Neeru Mittal
The document discusses C++ increment and decrement operators. It explains that these unary operators work only on integers, and can be used in both prefix (++a) and postfix (a++) forms. In prefix form, the increment/decrement occurs before the expression is evaluated. In postfix form, it occurs after. The key difference is that prefix returns the new value, while postfix returns the original value. Several examples are provided to illustrate this behavior. Finally, some practice questions are included to help test understanding of these fundamental operators.
Type casting is converting a variable from one data type to another. It is done explicitly using a cast operator like (type_name). It is best to cast to a higher data type to avoid data loss as casting to a lower type may truncate the value. There are two types of casting in C - implicit casting which happens automatically during assignment, and explicit casting which requires a cast operator. Implicit casting is done when assigning a value to a compatible type while explicit casting is needed when types are incompatible.
Type conversion in C provides two methods: implicit type conversion which occurs automatically during expressions, and explicit type conversion using cast expressions. Implicit conversion occurs when different types are used in expressions, such as when an int is used in a calculation with a float. The usual arithmetic conversions implicitly promote operands to the smallest type that can accommodate both values. Explicit casting uses cast operators to force a type conversion.
In computer science, a pointer is a programming language object, whose value refers to (or "points to") another value stored elsewhere in the computer memory using its memory address. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer.
C programming language supports two types of comments: single-line comments and multi-line comments. Single-line comments start with // and are used to comment individual statements. Multi-line comments start with /* and end with */ and can span multiple lines, making them useful for documentation at the beginning of code or for commenting blocks of code. Comments help explain the logic and flow of code but comments within comments are not allowed and will cause errors.
The document defines and describes various data types in the C programming language. It discusses integer data types like char, short int, int, long int; floating point data types like float, double, long double; void data type; and derived data types like arrays, pointers, structures, unions, enumerated data types, and user-defined data types using typedef. Each data type is explained along with its size, range of values it can hold, and examples.
This document discusses storage classes in the C programming language. It begins with an introduction to the C language and its history. The main body of the document then covers the four primary storage classes in C - automatic, register, static, and external. For each class, it provides details on storage location, default initial value, scope, and lifetime. Examples are provided to illustrate the behavior and usage of variables for each storage class. The key differences between the four classes are summarized in a table at the end.
Chapter1 c programming data types, variables and constantsvinay arora
The document discusses key concepts in C programming including:
- C is a general-purpose, procedural, portable programming language developed by Dennis Ritchie.
- Data types in C include integer, floating point, character, and string literals. Variables and constants can be declared with different data types.
- Variables store values that can change during program execution while constants store fixed values. Variables have both l-values and r-values but constants only have r-values.
- Comments, preprocessor directives, functions, and standard input/output are basic elements of a C program structure.
Programming in C - interview questions.pdfSergiuMatei7
C is a general-purpose programming language developed in the 1970s to develop the UNIX operating system. It produces very fast executable code and is widely used for system development work like operating systems, compilers, and network drivers. A basic C program consists of functions, variables, statements, expressions, preprocessor commands, and comments. It demonstrates a simple "Hello World" program that prints the message.
The document provides an introduction to algorithms and key concepts related to algorithms such as definition, features, examples, flowcharts, pseudocode. It also discusses different types of programming languages from first to fifth generation. Key points of structured programming approach and introduction to C programming language are explained including data types, variables, constants, input/output functions, operators, type conversion etc.
- Bitwise operators operate on individual bits of integer values and perform operations like AND, OR, XOR, and NOT.
- Negative integers are stored in two's complement form.
- Bitwise operators include & for AND, | for OR, ^ for XOR, ~ for NOT, << for left shift, >> for right shift, and >>> for unsigned right shift.
This document provides an overview of the C programming language. It begins with an outline of topics covered, then defines C as a structured, high-level, machine-independent language that follows a top-down approach. The document traces the history and evolution of C from earlier languages like ALGOL and BCPL. It describes key features of C like portability, speed, and simplicity. It also explains the roles of compilers and linkers and includes flowcharts, sample programs, and discussions of variables, data types, operators, and control statements in C like if/else statements and switch cases.
The document discusses the character set, keywords, and identifiers in the C programming language. It provides lists of uppercase and lowercase letters, digits, and special characters that are valid in C. It also lists and describes common keywords for data types, qualifiers, loop controls, user-defined types, jumping controls, and storage classes. Rules for writing identifiers are outlined, noting they must start with a letter, can include letters, digits, and underscores, and the first 31 characters are significant to the compiler.
Presentation on C++ Programming Languagesatvirsandhu9
This document provides an overview of the C++ programming language. It discusses why C++ is used, how it compares to Fortran, and the basic structure and components of a C++ program. The key topics covered include data types, variables, operators, selection statements, iteration statements, functions, arrays, pointers, input/output, preprocessor instructions, and comments. The document is intended to teach the basics of C++ programming in a structured way over multiple sections.
C++ is an object-oriented programming language that is an extension of C. It was developed in the 1980s to support object-oriented programming. In C++, data and functions can be combined into objects. Data in an object can only be accessed by the object's functions, allowing for encapsulation. The document then provides an overview of key C++ concepts like data types, tokens, operators, and input/output streams to introduce basic C++ syntax and programming.
This document discusses pointers in C++. It begins by defining pointers as variables that hold the memory addresses of other variables and explaining that pointers have types corresponding to the types of variables they point to. It then covers initializing and dereferencing pointers, constant pointers, pointer arithmetic, pointers and arrays, using pointers as function arguments, and memory management using pointers with the new and delete operators.
- An array is a collection of consecutive memory locations that all have the same name and type. An array allows storing multiple values of the same type using a single name.
- Arrays in C++ must be declared before use, specifying the type, name, and number of elements. Elements are accessed using an index.
- The main advantages of arrays are that they allow storing and processing large numbers of values efficiently using a single name. Arrays also make sorting and searching values easier.
This document provides an introduction to C++ programming. It discusses key differences between C and C++, shows simple C++ examples, and covers important C++ concepts like input/output streams, header files, inline functions, references, and reference parameters. The document is intended to teach basic C++ syntax and features to someone new to the language.
C Programming Language is the most popular computer language and most used programming language till now. It is very simple and elegant language. This lecture series will give you basic concepts of structured programming language with C.
The document discusses various data types in C++. It explains that data types define the type of data stored in variables and associated operations. There are fundamental data types like integer, character, float, double, and void provided by C++. User-defined data types include arrays, pointers, references, structures, unions, classes and enumerations. The document provides details on the size and range of standard data types like short int, int, long, float, double etc. It also explains various type modifiers and derived data types.
Increment and Decrement operators in C++Neeru Mittal
The document discusses C++ increment and decrement operators. It explains that these unary operators work only on integers, and can be used in both prefix (++a) and postfix (a++) forms. In prefix form, the increment/decrement occurs before the expression is evaluated. In postfix form, it occurs after. The key difference is that prefix returns the new value, while postfix returns the original value. Several examples are provided to illustrate this behavior. Finally, some practice questions are included to help test understanding of these fundamental operators.
Type casting is converting a variable from one data type to another. It is done explicitly using a cast operator like (type_name). It is best to cast to a higher data type to avoid data loss as casting to a lower type may truncate the value. There are two types of casting in C - implicit casting which happens automatically during assignment, and explicit casting which requires a cast operator. Implicit casting is done when assigning a value to a compatible type while explicit casting is needed when types are incompatible.
Type conversion in C provides two methods: implicit type conversion which occurs automatically during expressions, and explicit type conversion using cast expressions. Implicit conversion occurs when different types are used in expressions, such as when an int is used in a calculation with a float. The usual arithmetic conversions implicitly promote operands to the smallest type that can accommodate both values. Explicit casting uses cast operators to force a type conversion.
In computer science, a pointer is a programming language object, whose value refers to (or "points to") another value stored elsewhere in the computer memory using its memory address. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer.
C programming language supports two types of comments: single-line comments and multi-line comments. Single-line comments start with // and are used to comment individual statements. Multi-line comments start with /* and end with */ and can span multiple lines, making them useful for documentation at the beginning of code or for commenting blocks of code. Comments help explain the logic and flow of code but comments within comments are not allowed and will cause errors.
The document defines and describes various data types in the C programming language. It discusses integer data types like char, short int, int, long int; floating point data types like float, double, long double; void data type; and derived data types like arrays, pointers, structures, unions, enumerated data types, and user-defined data types using typedef. Each data type is explained along with its size, range of values it can hold, and examples.
This document discusses storage classes in the C programming language. It begins with an introduction to the C language and its history. The main body of the document then covers the four primary storage classes in C - automatic, register, static, and external. For each class, it provides details on storage location, default initial value, scope, and lifetime. Examples are provided to illustrate the behavior and usage of variables for each storage class. The key differences between the four classes are summarized in a table at the end.
Chapter1 c programming data types, variables and constantsvinay arora
The document discusses key concepts in C programming including:
- C is a general-purpose, procedural, portable programming language developed by Dennis Ritchie.
- Data types in C include integer, floating point, character, and string literals. Variables and constants can be declared with different data types.
- Variables store values that can change during program execution while constants store fixed values. Variables have both l-values and r-values but constants only have r-values.
- Comments, preprocessor directives, functions, and standard input/output are basic elements of a C program structure.
Programming in C - interview questions.pdfSergiuMatei7
C is a general-purpose programming language developed in the 1970s to develop the UNIX operating system. It produces very fast executable code and is widely used for system development work like operating systems, compilers, and network drivers. A basic C program consists of functions, variables, statements, expressions, preprocessor commands, and comments. It demonstrates a simple "Hello World" program that prints the message.
The document provides an introduction to algorithms and key concepts related to algorithms such as definition, features, examples, flowcharts, pseudocode. It also discusses different types of programming languages from first to fifth generation. Key points of structured programming approach and introduction to C programming language are explained including data types, variables, constants, input/output functions, operators, type conversion etc.
C is a widely used general-purpose programming language that can be used to develop complex software like operating systems and databases. It supports basic data types like integers, characters, and floating-point values. Constants are declared using the const keyword and cannot change value during program execution. C includes various operators like arithmetic, relational, logical, and bitwise operators to perform operations. Conditional statements and loops allow for control flow and repeated execution of code. Header files contain function declarations and macro definitions that can be included using the #include directive. Structures group related data types under a single name. Functions are blocks of code that perform tasks. Strings are arrays of characters terminated by a null character.
The document provides information about C language and its features. It discusses that C was developed by Dennis Ritchie in 1972 and is a general purpose programming language well suited for business and scientific applications. It also summarizes the basic structure of a C program and describes various C language components like data types, operators, and conditional statements.
C is a widely used general-purpose programming language that can be used to develop complex software like operating systems and databases. It has four basic data types - integer, character, floating-point, and double floating-point. Constants are declared using the const keyword and cannot change value during program execution. Operators perform actions on operands like arithmetic, relational, logical, and assignment operations. Conditional statements and loops allow control flow and repeated execution of code. Header files contain function declarations and macro definitions included using the #include directive. Structures group related variables under a single name. Functions perform specific tasks. Strings are arrays of characters terminated by a null character. C is a mid-level language providing both low-level and high
This document summarizes key elements of a C program structure including comments, preprocessor directives, global declarations, the main function, and constants. Comments are used to explain the program and are enclosed in /* */. Preprocessor directives like #include add functionality. Global variables are declared outside functions and accessible to all. The main function is where program execution begins, enclosed in braces. Constants refer to fixed values defined using #define or const.
C is a structured programming language developed by Dennis Ritchie in 1973 at Bell Laboratories. It was created to implement the UNIX operating system. C has features like being simple, portable, structured programming, a rich library, memory management, speed, pointers, recursion, and is a middle-level language. The basic structure of a C program includes documentation, link, definition, global declaration, main, and subprogram sections. It uses tokens, semicolons, comments, identifiers, keywords, and whitespace to structure the code.
The document provides an introduction to the C programming language. It discusses the structure of a C program including documentation, preprocessor directives, header files, and function definitions. It also describes various math and trigonometric functions available in the standard library like sqrt, pow, sin, cos, and log. The rest of the document outlines the steps to compile and execute a C program and defines key concepts like variables, constants, and data types in C.
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C is a general purpose programming language developed in the 1970s. It has features like control structures, looping statements, and arrays that make it well-suited for business and scientific applications. A C program executes in four steps - creating the program, compiling it, linking it to libraries, and executing the final executable file. C has keywords, variables, data types, operators, and conditional statements that allow for structured programming and control flow.
The document provides an introduction to the C programming language, covering its history, uses, basic concepts, and key functions. It discusses how C was created at Bell Labs to develop the UNIX operating system, its widespread adoption, and importance. The document outlines common C data types, control flow statements like conditionals and loops, functions and their structure, and input/output functions like printf, scanf, gets and puts. It provides examples of basic C programs and how functions, conditionals, and I/O are implemented.
C programming language tutorial for beginers.pdfComedyTechnology
This document provides an introduction and overview of the basics of C programming language. It discusses the following key topics in 3 or less sentences each:
- Introduction to programming and computer languages.
- Introduction to C programming, its history, uses, and why it is widely used.
- Program structure in C, including main functions, printf statements, comments, and return values.
- Basic syntax rules in C including semicolons, comments, identifiers, and whitespace.
- Common data types in C like char, int, float, and double and their purposes.
- How variables are named, defined through data type declaration, and initialized in C code.
- Common operators in
C is a general-purpose programming language developed at Bell Labs in the 1970s. It discusses the basics of C programming, including its history, structure, keywords, variables, data types, and provides an example "Hello World" program. The document provides an overview of the key elements of C for a beginner programmer to understand how to get started with C.
Learn c language Important topics ( Easy & Logical, & smart way of learning)Rohit Singh
Learn C language with an easy way including all important topics in C.
Learn c language Important topics ( Easy & Logical, & smart way of learning)
preprocessor Directive, Search Strategy, Header file, return 0 in C, return, main function, flow of execution, explicit return, function, return type and non return type function. Run- time Environment, type specifier, void keyword, 32 keyword in C, openning curly brace and closing curly brace, system library, single argument, String literal is an unnamed array with element of type char.
Diploma ii cfpc u-2 datatypes and variables in c languageRai University
The document discusses various topics related to C programming language such as basic structure of a C program, programming rules, comments, main method, declaration, data types, variables, operators, and conditional operators. It explains that a C program consists of functions organized into sections like documentation, definitions, global declarations, main function, and subprograms. It provides rules for writing comments, declaring variables, and defining valid identifiers and constants. It also describes various data types in C including integer, floating point, character, and string types.
Mca i pic u-2 datatypes and variables in c languageRai University
This document discusses various concepts related to data types and variables in the C programming language. It covers the basic structure of a C program and sections like documentation, definition, global declaration, main function, and subprogram sections. It describes rules for comments, the main method, declaration, data types like integer, floating point, character, and string. It also discusses variables, assigning values, and declaring variables with different storage classes.
This document provides an introduction to the C programming language, covering its history, uses, basic syntax, program structure, data types, variables, operators, and preprocessors. C was created in the 1970s by Dennis Ritchie at Bell Labs to develop the UNIX operating system. It is a general purpose, high-level language that produces efficient, structured programs and can handle both high-level and low-level activities. C is commonly used for operating systems, compilers, databases, and other modern programs. The document outlines the basic components needed to write C programs, including a compiler to translate human-readable source code into machine-executable code.
This document provides an overview of basic concepts in C programming including data types, variables, constants, and storage classes. It discusses the basic structure of a C program and sections like main(), functions, and declarations. It describes various data types in C like integer, float, character, and string. Rules for identifiers, keywords, and comments are also covered. The document explains variable declaration and assignment as well as constants like integer, real, character, string and escape sequences. Storage classes and scope of variables are discussed.
Btech i pic u-2 datatypes and variables in c languageRai University
This document discusses various topics related to C programming language including basic structure of a C program, programming rules, comments, main method, declaration, data types, variables, operators, and input/output functions. It explains that a C program contains functions organized into sections like main, documentation, definitions, and subprograms. It provides rules for writing comments, declaring and initializing variables, and defining valid identifiers. It also describes different data types in C like integer, float, character, and string. Finally, it discusses various operators supported in C for arithmetic, relational, logical, assignment, increment/decrement operations.
Bsc cs i pic u-2 datatypes and variables in c languageRai University
The document discusses various topics related to C programming language including basic structure of a C program, programming rules, comments, main method, declaration, data types, variables, operators, and conditional operators. It provides explanations and examples for each topic. The key points are that a C program contains functions organized into sections, all statements must end with a semicolon, comments are enclosed in /* */ , the main() function contains the main program logic, variables must be declared before use with a specified data type, and operators are used to manipulate variables and perform tasks like arithmetic, comparisons, assignments, and conditionals.
Software engineering is concerned with developing software using a systematic process and addressing factors like increasing demands and low expectations. It involves activities like specification, development, validation and evolution. Some key challenges are coping with diversity, reduced delivery times and developing trustworthy software. Different techniques are suitable depending on the type of system, and processes may incorporate elements of models like waterfall, incremental development and integration/configuration. Prototyping can help with requirements, design and testing.
The document provides an introduction to software engineering and discusses software, software engineering, the software development life cycle (SDLC), and SDLC models. It defines software and its components. It describes software engineering goals and challenges. It explains the SDLC phases including feasibility study, requirements analysis, design, development, testing, deployment, and maintenance. It discusses various SDLC models like waterfall, iterative, prototype, spiral, and agile models.
Software Engineering-Unit 2 "Requirement Engineering" by Adi.pdfProf. Dr. K. Adisesha
The document discusses requirement engineering and provides details on:
- Types of requirements including functional, non-functional, user, and system requirements
- The requirement engineering process including feasibility studies, elicitation, analysis, specification, validation, and management
- Software requirement specification (SRS) documents, their purpose, characteristics of a good SRS, and typical sections
- Functional and non-functional requirements in more depth
This document discusses system modeling. It defines system modeling as developing abstract models of a system from different perspectives. Common modeling techniques discussed include context models, interaction models, structural models, behavioral models, and model-driven engineering. Specific modeling languages covered are activity diagrams, use case diagrams, sequence diagrams, class diagrams, and state diagrams. The document provides examples and definitions for how to apply these modeling approaches and languages.
Architectural design establishes the framework for software development by examining requirements and designing a model that specifies system components, their inputs/outputs/functions, and interactions. It can be represented using structural, dynamic, process, functional, or framework models. The outputs are an architectural design document and various project plans. Architectural design decisions impact non-functional requirements and common decisions include architectural style and system decomposition.
The document discusses various types of software testing including unit testing, component testing, system testing, test-driven development, release testing, and user testing. It provides details on the goals and processes involved in each type of testing. Unit testing involves testing individual program units in isolation to check functionality. Component and system testing focus on interactions between units and components. Test-driven development interleaves writing tests before code. Release testing validates that software meets requirements before release. User testing involves customers providing input on a system under test.
This document discusses computer communication and networks. It defines data communication and its key characteristics of delivery, accuracy, timeliness and jitter. It describes the core components of a data communication system including the message, sender, receiver, transmission medium and protocols. It then discusses different types of computer networks including LANs, WANs, PANs and MANs. The key aspects covered are their definitions, examples, advantages and disadvantages.
Data communication involves the exchange of data between two devices via transmission media such as cables. It consists of five main components: a message, sender, receiver, transmission medium, and protocol. Data can be transmitted in three modes - simplex, half-duplex, and full-duplex. Transmission media can be guided (wired) such as twisted pair or coaxial cables, or unguided (wireless) such as radio waves. Networks are sets of connected devices that can be arranged in various topologies like bus, star, ring, or mesh. Switching techniques such as circuit, message, and packet switching determine how data is routed through a network.
The document discusses the data link layer. It covers the following key points:
- The data link layer has two sublayers: the logical link control (LLC) sublayer and the medium access control (MAC) sublayer.
- The LLC sublayer controls flow and performs error checking, while the MAC sublayer handles frame encapsulation and network addressing.
- The data link layer is responsible for framing, addressing, error control, flow control, and multi-access functionality. It takes packets and converts them to frames for transmission on the physical layer.
- Error detection techniques used include parity checks and cyclic redundancy checks to validate frames are transmitted accurately. Error correction can be done through retransmission
The document provides an overview of the network layer. It discusses key topics like the functions of the network layer such as logical addressing, routing, and internetworking. It describes different routing algorithms including distance vector, link state, and hierarchical routing. It also covers congestion control mechanisms like leaky bucket algorithm, token bucket algorithm, and admission control that are used to control congestion in the network layer.
The document discusses the transport and application layers of the OSI model. It begins by describing the transport layer, including its responsibilities of process-to-process delivery, end-to-end connections, multiplexing, congestion control, data integrity, error correction, and flow control. It then discusses the transport layer protocols TCP and UDP, comparing their key differences such as connection-oriented vs. connectionless and reliability. The document next covers application layer services and protocols, including DNS, HTTP, FTP, and email. It concludes by describing models like client-server and peer-to-peer that are used in application layer communication.
This document provides an introduction and overview of computer hardware components. It discusses input devices like keyboards, mice, scanners, and digital cameras. It also covers output devices such as monitors, printers, speakers. It describes different types of computers based on size and performance, such as microcomputers, minicomputers, and mainframes. The document then discusses computer memory, including primary memory technologies like RAM and ROM, as well as secondary magnetic storage.
This document provides an overview and introduction to the R programming language. It covers the history and development of R, which originated from the S language at Bell Labs in the 1970s. The document then outlines some key concepts in R including data structures, subsetting, control structures, functions, and debugging. It also discusses the design of the R system including its core functionality in base R and extensive library of additional packages.
The document discusses various government scholarship schemes in India and Karnataka for students. It outlines national schemes administered by ministries like Human Resource Development, Social Justice and Empowerment, Tribal Affairs and Minority Affairs. It also describes state-level schemes in Karnataka for SC/ST/OBC and minority students. Eligibility criteria include family income limits and minimum academic performance. The application process involves applying online through the National Scholarship Portal and State Scholarship Portal.
The document discusses various topics related to process management in operating systems, including:
1) A process is a program in execution that can be in different states like ready, running, waiting, or terminated. The OS uses a process control block to manage information for each process.
2) Processes communicate and synchronize access to shared resources using techniques like message passing and shared memory.
3) CPU scheduling algorithms like first-come first-served, shortest job next, priority, and round robin are used to allocate CPU time between ready processes.
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Information and Communication Technology in EducationMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 2)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
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Students will be able to explain the role and impact of Information and Communication Technology (ICT) in education. They will understand how ICT tools, such as computers, the internet, and educational software, enhance learning and teaching processes. By exploring various ICT applications, students will recognize how these technologies facilitate access to information, improve communication, support collaboration, and enable personalized learning experiences.
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐫𝐞𝐥𝐢𝐚𝐛𝐥𝐞 𝐬𝐨𝐮𝐫𝐜𝐞𝐬 𝐨𝐧 𝐭𝐡𝐞 𝐢𝐧𝐭𝐞𝐫𝐧𝐞𝐭:
-Students will be able to discuss what constitutes reliable sources on the internet. They will learn to identify key characteristics of trustworthy information, such as credibility, accuracy, and authority. By examining different types of online sources, students will develop skills to evaluate the reliability of websites and content, ensuring they can distinguish between reputable information and misinformation.
Images as attribute values in the Odoo 17Celine George
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C programming notes
1. C ProgrammingNotes
Prof. K. Adisesha 1
C Programming
Introduction
C programming is a general-purpose, procedural, imperative computer programming language
developed in 1972 by Dennis M. Ritchie at the Bell Telephone Laboratories to develop the UNIX
operating system. C is the most widely used computer language. It keeps fluctuating at number
one scale of popularity along with Java programming language, which is also equally popular and
most widely used among modern software programmers.
Facts about C
➢ C was invented to write an operating system called UNIX.
➢ C is a successor of B language which was introduced around the early 1970s.
➢ The language was formalized in 1988 by the American National Standard Institute (ANSI).
➢ The UNIX OS was totally written in C.
➢ Today C is the most widely used and popular System Programming Language.
➢ Most of the state-of-the-art software have been implemented using C.
Applications of C Programming
C was initially used for system development work, particularly the programs that make-up the
operating system. C was adopted as a system development language because it produces code that
runs nearly as fast as the code written in assembly language. Some examples of the use of C are -
➢ Operating Systems
➢ Language Compilers
➢ Assemblers
➢ Text Editors
➢ Print Spoolers
➢ Network Drivers
➢ Modern Programs
➢ Databases
➢ Language Interpreters
➢ Utilities
C Programs
A C program can vary from 3 lines to millions of lines and it should be written into one or more
text files with extension ".c"; for example, hello.c.
C - Program Structure
Before we study the basic building blocks of the C programming language, let us look at a bare
minimum C program structure so that we can take it as a reference in the upcoming chapters.
A C program basically consists of the following parts −
➢ Preprocessor Commands
➢ Functions
➢ Variables
➢ Statements & Expressions
➢ Comments
2. C ProgrammingNotes
Prof. K. Adisesha 2
Let us look at a simple code that would print the words "Hello World" −
#include <stdio.h>
int main()
{
/* my first program in C */
printf("Hello, World! n");
return 0;
}
Let us take a look at the various parts of the above program −
➢ The first line of the program #include <stdio.h> is a preprocessor command, which tells a
C compiler to include stdio.h file before going to actual compilation.
➢ The next line int main() is the main function where the program execution begins.
➢ The next line /*...*/ will be ignored by the compiler and it has been put to add additional
comments in the program. So such lines are called comments in the program.
➢ The next line printf(...) is another function available in C which causes the message "Hello,
World!" to be displayed on the screen.
➢ The next line return 0; terminates the main() function and returns the value 0.
C - Basic Syntax
You have seen the basic structure of a C program, so it will be easy to understand other basic
building blocks of the C programming language.
❖ Tokens in C
A C program consists of various tokens and a token is either a keyword, an identifier, a constant,
a string literal, or a symbol. For example, the following C statement consists of five tokens −
printf("Hello, World! n");
The individual tokens are −
printf
(
"Hello, World! n";
)
Semicolons ;
In a C program, the semicolon is a statement terminator. That is, each individual statement must
be ended with a semicolon. It indicates the end of one logical entity.
Given below are two different statements −
printf("Hello, World! n");
return 0;
Comments
Comments are like helping text in your C program and they are ignored by the compiler. They
start with /* and terminate with the characters */ as shown below −
/* my first program in C */
You cannot have comments within comments and they do not occur within a string or character
literals.
3. C ProgrammingNotes
Prof. K. Adisesha 3
Identifiers
A C identifier is a name used to identify a variable, function, or any other user-defined item. An
identifier starts with a letter A to Z, a to z, or an underscore '_' followed by zero or more letters,
underscores, and digits (0 to 9).
C does not allow punctuation characters such as @, $, and % within identifiers. C is a case-
sensitive programming language. Thus, Manpower and manpower are two different identifiers in
C. Here are some examples of acceptable identifiers −
mohd zara abc move_name a_123
myname50 _temp j a23b9 retVal
Keywords
The following list shows the reserved words in C. These reserved words may not be used as
constants or variables or any other identifier names.
auto else long switch
break enum register typedef
case extern return union
char float short unsigned
const for signed void
continue goto sizeof volatile
default if static while
do int struct _Packed
double
Whitespace in C
A line containing only whitespace, possibly with a comment, is known as a blank line, and a C
compiler totally ignores it.
Whitespace is the term used in C to describe blanks, tabs, newline characters and comments.
Whitespace separates one part of a statement from another and enables the compiler to identify
where one element in a statement, such as int, ends and the next element begins. Therefore, in the
following statement − int age;
C - Data Types
Data types in c refer to an extensive system used for declaring variables or functions of different
types. The type of a variable determines how much space it occupies in storage and how the bit
pattern stored is interpreted.
4. C ProgrammingNotes
Prof. K. Adisesha 4
The types in C can be classified as follows –
Sl.No. Types & Description
1 Basic Types: They are arithmetic types and are further classified into:
(a) integer types and (b) floating-point types.
2 Enumerated types: They are again arithmetic types and they are used to define variables
that can only assign certain discrete integer values throughout the program.
3 The type void: The type specifier void indicates that no value is available.
4 Derived types: They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union
types and (e) Function types.
Integer Types
The following table provides the details of standard integer types with their storage sizes and value
ranges −
Type Storage size Value range
char 1 byte -128 to 127 or 0 to 255
unsigned char 1 byte 0 to 255
signed char 1 byte -128 to 127
int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
long 8 bytes or (4bytes for
32 bit OS)
-9223372036854775808 to 9223372036854775807
unsigned long 8 bytes 0 to 18446744073709551615
Floating-Point Types
The following table provide the details of standard floating-point types with storage sizes and value
ranges and their precision –
5. C ProgrammingNotes
Prof. K. Adisesha 5
Type Storage size Value range Precision
float 4 byte 1.2E-38 to 3.4E+38 6 decimal places
double 8 byte 2.3E-308 to 1.7E+308 15 decimal places
long double 10 byte 3.4E-4932 to 1.1E+4932 19 decimal places
The void Type
The void type specifies that no value is available. It is used in three kinds of situations –
Sl.No. Types & Description
1 Function returns as void: There are various functions in C which do not return any value
or you can say they return void. A function with no return value has the return type as void.
For example, void exit (int status);
2 Function arguments as void: There are various functions in C which do not accept any
parameter. A function with no parameter can accept a void. For example, int rand(void);
3 Pointers to void: A pointer of type void * represents the address of an object, but not its
type. For example, a memory allocation function void *malloc (size_t size); returns a pointer
to void which can be casted to any data type.
C - Variables
A variable is nothing but a name given to a storage area that our programs can manipulate. Each
variable in C has a specific type, which determines the size and layout of the variable's memory;
the range of values that can be stored within that memory; and the set of operations that can be
applied to the variable.
The name of a variable can be composed of letters, digits, and the underscore character. It must
begin with either a letter or an underscore. Upper and lowercase letters are distinct because C is
case-sensitive.
The following basic variable types –
Sl.No. Type & Description
1 Char: Typically a single octet(one byte). It is an integer type.
2 Int: The most natural size of integer for the machine.
6. C ProgrammingNotes
Prof. K. Adisesha 6
3 Float: A single-precision floating point value.
4 Double: A double-precision floating point value.
5 Void: Represents the absence of type.
C programming language also allows to define various other types of variables, which we will
cover in subsequent chapters like Enumeration, Pointer, Array, Structure, Union, etc. For this
chapter, let us study only basic variable types.
Variable Definition in C
A variable definition tells the compiler where and how much storage to create for the variable. A
variable definition specifies a data type and contains a list of one or more variables of that type as
follows − type variable_list;
Here, type must be a valid C data type including char, w_char, int, float, double, bool, or any user-
defined object; and variable_list may consist of one or more identifier names separated by
commas. Some valid declarations are shown here −
int i, j, k;
char c, ch;
float f, salary;
double d;
The line int i, j, k; declares and defines the variables i, j, and k; which instruct the compiler to
create variables named i, j and k of type int.
Variables can be initialized (assigned an initial value) in their declaration. The initializer consists
of an equal sign followed by a constant expression as follows −
type variable_name = value;
Some examples are −
extern int d = 3, f = 5; // declaration of d and f.
int d = 3, f = 5; // definition and initializing d and f.
byte z = 22; // definition and initializes z.
char x = 'x'; // the variable x has the value 'x'.
For definition without an initializer: variables with static storage duration are implicitly initialized
with NULL (all bytes have the value 0); the initial value of all other variables are undefined.
Lvalues and Rvalues in C
There are two kinds of expressions in C −
7. C ProgrammingNotes
Prof. K. Adisesha 7
➢ lvalue − Expressions that refer to a memory location are called "lvalue" expressions. An lvalue
may appear as either the left-hand or right-hand side of an assignment.
➢ rvalue − The term rvalue refers to a data value that is stored at some address in memory. An
rvalue is an expression that cannot have a value assigned to it which means an rvalue may
appear on the right-hand side but not on the left-hand side of an assignment.
Variables are lvalues and so they may appear on the left-hand side of an assignment. Numeric
literals are rvalues and so they may not be assigned and cannot appear on the left-hand side. Take
a look at the following valid and invalid statements −
int g = 20; // valid statement
10 = 20; // invalid statement; would generate compile-time error
Constants
Constants refer to fixed values that the program may not alter during its execution. These fixed
values are also called literals.
Constants can be of any of the basic data types like an integer constant, a floating constant, a
character constant, or a string literal. There are enumeration constants as well.
Constants are treated just like regular variables except that their values cannot be modified after
their definition.
❖ Integer Literals
An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies the base or
radix: 0x or 0X for hexadecimal, 0 for octal, and nothing for decimal.
An integer literal can also have a suffix that is a combination of U and L, for unsigned and long,
respectively. The suffix can be uppercase or lowercase and can be in any order.
Here are some examples of integer literals −
212 /* Legal */
215u /* Legal */
0xFeeL /* Legal */
078 /* Illegal: 8 is not an octal digit */
032UU /* Illegal: cannot repeat a suffix */
Following are other examples of various types of integer literals −
85 /* decimal */
0213 /* octal */
0x4b /* hexadecimal */
30 /* int */
30u /* unsigned int */
30l /* long */
30ul /* unsigned long */
❖ Floating-point Literals
A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent part.
You can represent floating point literals either in decimal form or exponential form.
8. C ProgrammingNotes
Prof. K. Adisesha 8
While representing decimal form, you must include the decimal point, the exponent, or both; and
while representing exponential form, you must include the integer part, the fractional part, or both.
The signed exponent is introduced by e or E.
Here are some examples of floating-point literals −
3.14159 /* Legal */
314159E-5L /* Legal */
510E /* Illegal: incomplete exponent */
210f /* Illegal: no decimal or exponent */
.e55 /* Illegal: missing integer or fraction */
❖ Character Constants
Character literals are enclosed in single quotes, e.g., 'x' can be stored in a simple variable
of char type.
A character literal can be a plain character (e.g., 'x'), an escape sequence (e.g., 't'), or a universal
character (e.g., 'u02C0').
There are certain characters in C that represent special meaning when preceded by a backslash for
example, newline (n) or tab (t). Following is the example to show a few escape sequence
characters −
#include <stdio.h>
int main()
{
printf("HellotWorldnn");
return 0;
}
❖ String Literals
String literals or constants are enclosed in double quotes "". A string contains characters that are
similar to character literals: plain characters, escape sequences, and universal characters.
You can break a long line into multiple lines using string literals and separating them using white
spaces.
Here are some examples of string literals. All the three forms are identical strings.
"hello, dear"
"hello, dear"
"hello, " "d" "ear"
Defining Constants
There are two simple ways in C to define constants −
➢ Using #define preprocessor.
➢ Using const keyword.
❖ The #define Preprocessor
Given below is the form to use #define preprocessor to define a constant −
#define identifier value
The following example explains it in detail −
#include <stdio.h>
9. C ProgrammingNotes
Prof. K. Adisesha 9
#define LENGTH 10
#define WIDTH 5
#define NEWLINE 'n'
int main() {
int area;
area = LENGTH * WIDTH;
printf("value of area : %d", area);
printf("%c", NEWLINE);
return 0;
}
When the above code is compiled and executed, it produces the following result − value of area :
50
❖ The const Keyword
You can use const prefix to declare constants with a specific type as follows −
const type variable = value;
The following example explains it in detail −
#include <stdio.h>
int main() {
const int LENGTH = 10;
const int WIDTH = 5;
const char NEWLINE = 'n';
int area;
area = LENGTH * WIDTH;
printf("value of area : %d", area);
printf("%c", NEWLINE);
return 0;
}
When the above code is compiled and executed, it produces the following result − value of area :
50
C - Storage Classes
A storage class defines the scope (visibility) and life-time of variables and/or functions within a C
Program. They precede the type that they modify. We have four different storage classes in a C
program −
➢ auto
➢ register
➢ static
➢ extern
❖ The auto Storage Class
The auto storage class is the default storage class for all local variables.
{
int mount;
auto int month;
10. C ProgrammingNotes
Prof. K. Adisesha 10
}
The example above defines two variables with in the same storage class. 'auto' can only be used
within functions, i.e., local variables.
❖ The register Storage Class
The register storage class is used to define local variables that should be stored in a register instead
of RAM. This means that the variable has a maximum size equal to the register size (usually one
word) and can't have the unary '&' operator applied to it (as it does not have a memory location).
{
register int miles;
}
The register should only be used for variables that require quick access such as counters. It should
also be noted that defining 'register' does not mean that the variable will be stored in a register. It
means that it MIGHT be stored in a register depending on hardware and implementation
restrictions.
❖ The static Storage Class
The static storage class instructs the compiler to keep a local variable in existence during the life-
time of the program instead of creating and destroying it each time it comes into and goes out of
scope. Therefore, making local variables static allows them to maintain their values between
function calls.
The static modifier may also be applied to global variables. When this is done, it causes that
variable's scope to be restricted to the file in which it is declared.
In C programming, when static is used on a global variable, it causes only one copy of that member
to be shared by all the objects of its class.
#include <stdio.h>
/* function declaration */
void func(void);
static int count = 5; /* global variable */
main() {
while(count--) {
func();
}
return 0;
}
/* function definition */
void func( void ) {
static int i = 5; /* local static variable */
i++;
printf("i is %d and count is %dn", i, count);
}
When the above code is compiled and executed, it produces the following result −
i is 6 and count is 4
11. C ProgrammingNotes
Prof. K. Adisesha 11
i is 7 and count is 3
i is 8 and count is 2
i is 9 and count is 1
i is 10 and count is 0
❖ The extern Storage Class
The extern storage class is used to give a reference of a global variable that is visible to ALL the
program files. When you use 'extern', the variable cannot be initialized however, it points the
variable name at a storage location that has been previously defined.
When you have multiple files and you define a global variable or function, which will also be used
in other files, then extern will be used in another file to provide the reference of defined variable
or function. Just for understanding, extern is used to declare a global variable or function in another
file.
The extern modifier is most commonly used when there are two or more files sharing the same
global variables or functions as explained below.
First File: main.c
#include <stdio.h>
int count ;
extern void write_extern();
main() {
count = 5;
write_extern();
}
Second File: support.c
#include <stdio.h>
extern int count;
void write_extern(void) {
printf("count is %dn", count);
}
Here, extern is being used to declare count in the second file, where as it has its definition in the
first file, main.c. Now, compile these two files as follows −
$gcc main.c support.c
It will produce the executable program a.out. When this program is executed, it produces the
following result −
count is 5
C - Operators
An operator is a symbol that tells the compiler to perform specific mathematical or logical
functions. C language is rich in built-in operators and provides the following types of operators −
➢ Arithmetic Operators
➢ Relational Operators
➢ Logical Operators
➢ Bitwise Operators
➢ Assignment Operators
12. C ProgrammingNotes
Prof. K. Adisesha 12
➢ Misc Operators
❖ Arithmetic Operators
The following table shows all the arithmetic operators supported by the C language. Assume
variable A holds 10 and variable B holds 20 then –
Show Examples
Operator Description Example
+ Adds two operands. A + B = 30
− Subtracts second operand from the first. A − B = -10
* Multiplies both operands. A * B = 200
/ Divides numerator by de-numerator. B / A = 2
% Modulus Operator and remainder of after an integer division. B % A = 0
++ Increment operator increases the integer value by one. A++ = 11
-- Decrement operator decreases the integer value by one. A-- = 9
❖ Relational Operators
The following table shows all the relational operators supported by C. Assume variable A holds
10 and variable B holds 20 then −
Show Examples
Operator Description Example
== Checks if the values of two operands are equal or not. If yes, then
the condition becomes true.
(A == B) is not true.
!= Checks if the values of two operands are equal or not. If the values
are not equal, then the condition becomes true.
(A != B) is true.
> Checks if the value of left operand is greater than the value of right
operand. If yes, then the condition becomes true.
(A > B) is not true.
< Checks if the value of left operand is less than the value of right
operand. If yes, then the condition becomes true.
(A < B) is true.
13. C ProgrammingNotes
Prof. K. Adisesha 13
>= Checks if the value of left operand is greater than or equal to the
value of right operand. If yes, then the condition becomes true.
(A >= B) is not true.
<= Checks if the value of left operand is less than or equal to the value
of right operand. If yes, then the condition becomes true.
(A <= B) is true.
❖ Logical Operators
Following table shows all the logical operators supported by C language. Assume variable A holds
1 and variable B holds 0, then −
Show Examples
Operator Description Example
&& Called Logical AND operator. If both the operands are non-zero,
then the condition becomes true.
(A && B) is false.
|| Called Logical OR Operator. If any of the two operands is non-zero,
then the condition becomes true.
(A || B) is true.
! Called Logical NOT Operator. It is used to reverse the logical state
of its operand. If a condition is true, then Logical NOT operator will
make it false.
!(A && B) is true.
❖ Bitwise Operators
Bitwise operator works on bits and perform bit-by-bit operation. The truth tables for &, |, and ^ is
as follows −
p q p & q p | q p ^ q
0 0 0 0 0
0 1 0 1 1
1 1 1 1 0
1 0 0 1 1
Assume A = 60 and B = 13 in binary format, they will be as follows −
A = 0011 1100
B = 0000 1101
-----------------
A&B = 0000 1100
A|B = 0011 1101
A^B = 0011 0001
~A = 1100 0011
14. C ProgrammingNotes
Prof. K. Adisesha 14
The following table lists the bitwise operators supported by C. Assume variable 'A' holds 60 and
variable 'B' holds 13, then –
Show Examples
Operator Description Example
& Binary AND Operator copies a bit to the result if it exists
in both operands.
(A & B) = 12, i.e., 0000 1100
| Binary OR Operator copies a bit if it exists in either
operand.
(A | B) = 61, i.e., 0011 1101
^ Binary XOR Operator copies the bit if it is set in one
operand but not both.
(A ^ B) = 49, i.e., 0011 0001
~ Binary One's Complement Operator is unary and has the
effect of 'flipping' bits.
(~A ) = ~(60), i.e,. -0111101
<< Binary Left Shift Operator. The left operands value is
moved left by the number of bits specified by the right
operand.
A << 2 = 240 i.e., 1111 0000
>> Binary Right Shift Operator. The left operands value is
moved right by the number of bits specified by the right
operand.
A >> 2 = 15 i.e., 0000 1111
❖ Assignment Operators
The following table lists the assignment operators supported by the C language –
Show Examples
Operator Description Example
= Simple assignment operator. Assigns values from
right side operands to left side operand
C = A + B will assign the value of A
+ B to C
+= Add AND assignment operator. It adds the right
operand to the left operand and assign the result to
the left operand.
C += A is equivalent to C = C + A
-= Subtract AND assignment operator. It subtracts the
right operand from the left operand and assigns the
result to the left operand.
C -= A is equivalent to C = C - A
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*= Multiply AND assignment operator. It multiplies
the right operand with the left operand and assigns
the result to the left operand.
C *= A is equivalent to C = C * A
/= Divide AND assignment operator. It divides the left
operand with the right operand and assigns the
result to the left operand.
C /= A is equivalent to C = C / A
%= Modulus AND assignment operator. It takes
modulus using two operands and assigns the result
to the left operand.
C %= A is equivalent to C = C % A
<<= Left shift AND assignment operator. C <<= 2 is same as C = C << 2
>>= Right shift AND assignment operator. C >>= 2 is same as C = C >> 2
&= Bitwise AND assignment operator. C &= 2 is same as C = C & 2
^= Bitwise exclusive OR and assignment operator. C ^= 2 is same as C = C ^ 2
|= Bitwise inclusive OR and assignment operator. C |= 2 is same as C = C | 2
❖ Misc Operators ↦ sizeof & ternary
Besides the operators discussed above, there are a few other important operators
including sizeof and ? : supported by the C Language.
Show Examples
Operator Description Example
sizeof() Returns the size of a variable. sizeof(a), where a is integer, will return 4.
& Returns the address of a variable. &a; returns the actual address of the variable.
* Pointer to a variable. *a;
? : Conditional Expression. If Condition is true ? then value X : otherwise value Y
Operators Precedence in C
Operator precedence determines the grouping of terms in an expression and decides how an
expression is evaluated. Certain operators have higher precedence than others; for example, the
multiplication operator has a higher precedence than the addition operator.
For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has a higher precedence
than +, so it first gets multiplied with 3*2 and then adds into 7.
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Here, operators with the highest precedence appear at the top of the table, those with the lowest
appear at the bottom. Within an expression, higher precedence operators will be evaluated first.
Show Examples
Category Operator Associativity
Postfix () [] -> . ++ - - Left to right
Unary + - ! ~ ++ - - (type)* & sizeof Right to left
Multiplicative * / % Left to right
Additive + - Left to right
Shift << >> Left to right
Relational < <= > >= Left to right
Equality == != Left to right
Bitwise AND & Left to right
Bitwise XOR ^ Left to right
Bitwise OR | Left to right
Logical AND && Left to right
Logical OR || Left to right
Conditional ?: Right to left
Assignment = += -= *= /= %=>>= <<= &= ^= |= Right to left
Comma , Left to right
C - Decision Making
Decision making structures require that the programmer specifies one or more conditions to be
evaluated or tested by the program, along with a statement or statements to be executed if the
condition is determined to be true, and optionally, other statements to be executed if the condition
is determined to be false.
Show below is the general form of a typical decision making structure found in most of the
programming languages −
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C programming language assumes any non-zero and non-null values as true, and if it is
either zero or null, then it is assumed as false value.
C programming language provides the following types of decision making statements.
Sl.No. Statement & Description
1 if statement
An if statement consists of a boolean expression followed by one or more statements.
2 if...else statement
An if statement can be followed by an optional else statement, which executes when the
Boolean expression is false.
3 nested if statements
You can use one if or else if statement inside another if or else if statement(s).
4 switch statement
A switch statement allows a variable to be tested for equality against a list of values.
5 nested switch statements
You can use one switch statement inside another switch statement(s).
The ? : Operator
We have covered conditional operator ? : in the previous chapter which can be used to
replace if...else statements. It has the following general form −
Exp1 ? Exp2 : Exp3;
Where Exp1, Exp2, and Exp3 are expressions. Notice the use and placement of the colon.
The value of a ? expression is determined like this −
➢ Exp1 is evaluated. If it is true, then Exp2 is evaluated and becomes the value of the entire
? expression.
➢ If Exp1 is false, then Exp3 is evaluated and its value becomes the value of the expression.
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C - Loops
You may encounter situations, when a block of code needs to be executed several number of times.
In general, statements are executed sequentially: The first statement in a function is executed first,
followed by the second, and so on.
Programming languages provide various control structures that allow for more complicated
execution paths.
A loop statement allows us to execute a statement or group of statements multiple times. Given
below is the general form of a loop statement in most of the programming languages −
C programming language provides the following types of loops to handle looping requirements.
Sl.No. Loop Type & Description
1 while loop
Repeats a statement or group of statements while a given condition is true. It tests the
condition before executing the loop body.
2 for loop
Executes a sequence of statements multiple times and abbreviates the code that manages the
loop variable.
3 do...while loop
It is more like a while statement, except that it tests the condition at the end of the loop body.
4 nested loops
You can use one or more loops inside any other while, for, or do..while loop.
Loop Control Statements
Loop control statements change execution from its normal sequence. When execution leaves a
scope, all automatic objects that were created in that scope are destroyed.
C supports the following control statements.
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Sr.No. Control Statement & Description
1 break statement
Terminates the loop or switch statement and transfers execution to the statement
immediately following the loop or switch.
2 continue statement
Causes the loop to skip the remainder of its body and immediately retest its condition prior
to reiterating.
3 goto statement
Transfers control to the labeled statement.
The Infinite Loop
A loop becomes an infinite loop if a condition never becomes false. The for loop is traditionally
used for this purpose. Since none of the three expressions that form the 'for' loop are required, you
can make an endless loop by leaving the conditional expression empty.
#include <stdio.h>
int main () {
for( ; ; ) {
printf("This loop will run forever.n");
}
return 0;
}
When the conditional expression is absent, it is assumed to be true. You may have an initialization
and increment expression, but C programmers more commonly use the for(;;) construct to signify
an infinite loop.
C - Functions
A function is a group of statements that together perform a task. Every C program has at least one
function, which is main(), and all the most trivial programs can define additional functions.
You can divide up your code into separate functions. How you divide up your code among different
functions is up to you, but logically the division is such that each function performs a specific task.
A function declaration tells the compiler about a function's name, return type, and parameters. A
function definition provides the actual body of the function.
The C standard library provides numerous built-in functions that your program can call. For
example, strcat() to concatenate two strings, memcpy() to copy one memory location to another
location, and many more functions.
A function can also be referred as a method or a sub-routine or a procedure, etc.
Defining a Function
The general form of a function definition in C programming language is as follows −
return_type function_name( parameter list ) {
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body of the function
}
A function definition in C programming consists of a function header and a function body.
Here are all the parts of a function −
❖ Return Type − A function may return a value. The return_type is the data type of the value
the function returns. Some functions perform the desired operations without returning a value.
In this case, the return_type is the keyword void.
❖ Function Name − This is the actual name of the function. The function name and the
parameter list together constitute the function signature.
❖ Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value
to the parameter. This value is referred to as actual parameter or argument. The parameter list
refers to the type, order, and number of the parameters of a function. Parameters are optional;
that is, a function may contain no parameters.
❖ Function Body − The function body contains a collection of statements that define what the
function does.
Example
Given below is the source code for a function called max(). This function takes two parameters
num1 and num2 and returns the maximum value between the two −
/* function returning the max between two numbers */
int max(int num1, int num2) {
/* local variable declaration */
int result;
if (num1 > num2)
result = num1;
else
result = num2;
return result;
}
Function Declarations
A function declaration tells the compiler about a function name and how to call the function. The
actual body of the function can be defined separately.
A function declaration has the following parts −
return_type function_name( parameter list );
For the above defined function max(), the function declaration is as follows −
int max(int num1, int num2);
Parameter names are not important in function declaration only their type is required, so the
following is also a valid declaration −
int max(int, int);
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Function declaration is required when you define a function in one source file and you call that
function in another file. In such case, you should declare the function at the top of the file calling
the function.
Calling a Function
While creating a C function, you give a definition of what the function has to do. To use a function,
you will have to call that function to perform the defined task.
When a program calls a function, the program control is transferred to the called function. A called
function performs a defined task and when its return statement is executed or when its function-
ending closing brace is reached, it returns the program control back to the main program.
To call a function, you simply need to pass the required parameters along with the function name,
and if the function returns a value, then you can store the returned value. For example −
#include <stdio.h>
/* function declaration */
int max(int num1, int num2);
int main () {
/* local variable definition */
int a = 100;
int b = 200;
int ret;
/* calling a function to get max value */
ret = max(a, b);
printf( "Max value is : %dn", ret );
return 0;
}
/* function returning the max between two numbers */
int max(int num1, int num2) {
/* local variable declaration */
int result;
if (num1 > num2)
result = num1;
else
result = num2;
return result;
}
We have kept max() along with main() and compiled the source code. While running the final
executable, it would produce the following result −
Max value is : 200
Function Arguments
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If a function is to use arguments, it must declare variables that accept the values of the arguments.
These variables are called the formal parameters of the function.
Formal parameters behave like other local variables inside the function and are created upon entry
into the function and destroyed upon exit.
While calling a function, there are two ways in which arguments can be passed to a function −
Sl.No. Call Type & Description
1 Call by value
This method copies the actual value of an argument into the formal parameter of the function.
In this case, changes made to the parameter inside the function have no effect on the
argument.
2 Call by reference
This method copies the address of an argument into the formal parameter. Inside the function,
the address is used to access the actual argument used in the call. This means that changes
made to the parameter affect the argument.
By default, C uses call by value to pass arguments. In general, it means the code within a function
cannot alter the arguments used to call the function.
C - Scope Rules
A scope in any programming is a region of the program where a defined variable can have its
existence and beyond that variable it cannot be accessed. There are three places where variables
can be declared in C programming language −
➢ Inside a function or a block which is called local variables.
➢ Outside of all functions which is called global variables.
In the definition of function parameters which are called formal parameters.
Let us understand what are local and global variables, and formal parameters.
❖ Local Variables
Variables that are declared inside a function or block are called local variables. They can be used
only by statements that are inside that function or block of code. Local variables are not known to
functions outside their own. The following example shows how local variables are used. Here all
the variables a, b, and c are local to main() function.
#include <stdio.h>
int main () {
/* local variable declaration */
int a, b;
int c;
/* actual initialization */
a = 10;
b = 20;
c = a + b;
printf ("value of a = %d, b = %d and c = %dn", a, b, c);
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return 0;
}
❖ Global Variables
Global variables are defined outside a function, usually on top of the program. Global variables
hold their values throughout the lifetime of your program and they can be accessed inside any of
the functions defined for the program.
A global variable can be accessed by any function. That is, a global variable is available for use
throughout your entire program after its declaration. The following program show how global
variables are used in a program.
#include <stdio.h>
/* global variable declaration */
int g;
int main () {
/* local variable declaration */
int a, b;
/* actual initialization */
a = 10;
b = 20;
g = a + b;
printf ("value of a = %d, b = %d and g = %dn", a, b, g);
return 0;
}
A program can have same name for local and global variables but the value of local variable inside
a function will take preference. Here is an example −
#include <stdio.h>
/* global variable declaration */
int g = 20;
int main () {
/* local variable declaration */
int g = 10;
printf ("value of g = %dn", g);
return 0;
}
When the above code is compiled and executed, it produces the following result −value of g = 10
❖ Formal Parameters
Formal parameters, are treated as local variables with-in a function and they take precedence over
global variables. Following is an example −
#include <stdio.h>
/* global variable declaration */
int a = 20;
int main () {
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/* local variable declaration in main function */
int a = 10;
int b = 20;
int c = 0;
printf ("value of a in main() = %dn", a);
c = sum( a, b);
printf ("value of c in main() = %dn", c);
return 0;
}
/* function to add two integers */
int sum(int a, int b) {
printf ("value of a in sum() = %dn", a);
printf ("value of b in sum() = %dn", b);
return a + b;
}
When the above code is compiled and executed, it produces the following result −
value of a in main() = 10
value of a in sum() = 10
value of b in sum() = 20
value of c in main() = 30
Initializing Local and Global Variables
When a local variable is defined, it is not initialized by the system, you must initialize it yourself.
Global variables are initialized automatically by the system when you define them as follows −
Data Type Initial Default Value
int 0
char '0'
float 0
double 0
pointer NULL
It is a good programming practice to initialize variables properly, otherwise your program may
produce unexpected results, because uninitialized variables will take some garbage value already
available at their memory location.
C - Arrays
Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the
same type. An array is used to store a collection of data, but it is often more useful to think of an
array as a collection of variables of the same type.
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Instead of declaring individual variables, such as number0, number1, ..., and number99, you
declare one array variable such as numbers and use numbers[0], numbers[1], and ..., numbers[99]
to represent individual variables. A specific element in an array is accessed by an index.
All arrays consist of contiguous memory locations. The lowest address corresponds to the first
element and the highest address to the last element.
Declaring Arrays
To declare an array in C, a programmer specifies the type of the elements and the number of
elements required by an array as follows −
type arrayName [ arraySize ];
This is called a single-dimensional array. The arraySize must be an integer constant greater than
zero and type can be any valid C data type. For example, to declare a 10-element array
called balance of type double, use this statement −
double balance[10];
Here balance is a variable array which is sufficient to hold up to 10 double numbers.
Initializing Arrays
You can initialize an array in C either one by one or using a single statement as follows −
double balance[5] = {1000.0, 2.0, 3.4, 7.0, 50.0};
The number of values between braces { } cannot be larger than the number of elements that we
declare for the array between square brackets [ ].
If you omit the size of the array, an array just big enough to hold the initialization is created.
Therefore, if you write −
double balance[] = {1000.0, 2.0, 3.4, 7.0, 50.0};
You will create exactly the same array as you did in the previous example. Following is an example
to assign a single element of the array −
balance[4] = 50.0;
The above statement assigns the 5th
element in the array with a value of 50.0. All arrays have 0 as
the index of their first element which is also called the base index and the last index of an array
will be total size of the array minus 1. Shown below is the pictorial representation of the array we
discussed above −
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Accessing Array Elements
An element is accessed by indexing the array name. This is done by placing the index of the
element within square brackets after the name of the array. For example −
double salary = balance[9];
The above statement will take the 10th
element from the array and assign the value to salary
variable. The following example Shows how to use all the three above mentioned concepts viz.
declaration, assignment, and accessing arrays −
#include <stdio.h>
int main () {
int n[ 10 ]; /* n is an array of 10 integers */
int i,j;
/* initialize elements of array n to 0 */
for ( i = 0; i < 10; i++ ) {
n[ i ] = i + 100; /* set element at location i to i + 100 */
}
/* output each array element's value */
for (j = 0; j < 10; j++ ) {
printf("Element[%d] = %dn", j, n[j] );
}
return 0;
}
When the above code is compiled and executed, it produces the following result −
Element[0] = 100
Element[1] = 101
Element[2] = 102
Element[3] = 103
Element[4] = 104
Element[5] = 105
Element [6] = 106
Element [7] = 107
Element [8] = 108
Element [9] = 109
Arrays in Detail
Arrays are important to C and should need a lot more attention. The following important concepts
related to array should be clear to a C programmer –
Sr.No. Concept & Description
1 Multi-dimensional arrays
C supports multidimensional arrays. The simplest form of the multidimensional array is
the two-dimensional array.
2 Passing arrays to functions
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You can pass to the function a pointer to an array by specifying the array's name without
an index.
3 Return array from a function
C allows a function to return an array.
4 Pointer to an array
You can generate a pointer to the first element of an array by simply specifying the array
name, without any index.
C - Pointers
Pointers in C are easy and fun to learn. Some C programming tasks are performed more easily
with pointers, and other tasks, such as dynamic memory allocation, cannot be performed without
using pointers. So it becomes necessary to learn pointers to become a perfect C programmer. Let's
start learning them in simple and easy steps.
As you know, every variable is a memory location and every memory location has its address
defined which can be accessed using ampersand (&) operator, which denotes an address in
memory. Consider the following example, which prints the address of the variables defined −
#include <stdio.h>
int main ()
{
int var1;
char var2[10];
printf("Address of var1 variable: %xn", &var1 );
printf("Address of var2 variable: %xn", &var2 );
return 0;
}
When the above code is compiled and executed, it produces the following result −
Address of var1 variable: bff5a400
Address of var2 variable: bff5a3f6
Pointers
A pointer is a variable whose value is the address of another variable, i.e., direct address of the
memory location. Like any variable or constant, you must declare a pointer before using it to store
any variable address. The general form of a pointer variable declaration is −
type *var-name;
Here, type is the pointer's base type; it must be a valid C data type and var-name is the name of the
pointer variable. The asterisk * used to declare a pointer is the same asterisk used for
multiplication. However, in this statement the asterisk is being used to designate a variable as a
pointer. Take a look at some of the valid pointer declarations −
int *ip; /* pointer to an integer */
double *dp; /* pointer to a double */
float *fp; /* pointer to a float */
char *ch /* pointer to a character */
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The actual data type of the value of all pointers, whether integer, float, character, or otherwise, is
the same, a long hexadecimal number that represents a memory address. The only difference
between pointers of different data types is the data type of the variable or constant that the pointer
points to.
How to Use Pointers?
There are a few important operations, which we will do with the help of pointers very
frequently. (a) We define a pointer variable, (b) assign the address of a variable to a pointer
and (c) finally access the value at the address available in the pointer variable. This is done by
using unary operator * that returns the value of the variable located at the address specified by its
operand. The following example makes use of these operations −
#include <stdio.h>
int main () {
int var = 20; /* actual variable declaration */
int *ip; /* pointer variable declaration */
ip = &var; /* store address of var in pointer variable*/
printf("Address of var variable: %xn", &var );
/* address stored in pointer variable */
printf("Address stored in ip variable: %xn", ip );
/* access the value using the pointer */
printf("Value of *ip variable: %dn", *ip );
return 0;
}
When the above code is compiled and executed, it produces the following result −
Address of var variable: bffd8b3c
Address stored in ip variable: bffd8b3c
Value of *ip variable: 20
NULL Pointers
It is always a good practice to assign a NULL value to a pointer variable in case you do not have
an exact address to be assigned. This is done at the time of variable declaration. A pointer that is
assigned NULL is called a null pointer.
The NULL pointer is a constant with a value of zero defined in several standard libraries. Consider
the following program −
#include <stdio.h>
int main () {
int *ptr = NULL;
printf("The value of ptr is : %xn", ptr );
return 0;
}
When the above code is compiled and executed, it produces the following result −
The value of ptr is 0
In most of the operating systems, programs are not permitted to access memory at address 0
because that memory is reserved by the operating system. However, the memory address 0 has
special significance; it signals that the pointer is not intended to point to an accessible memory
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location. But by convention, if a pointer contains the null (zero) value, it is assumed to point to
nothing.
To check for a null pointer, you can use an 'if' statement as follows −
if(ptr) /* succeeds if p is not null */
if(!ptr) /* succeeds if p is null */
Pointers in Detail
Pointers have many but easy concepts and they are very important to C programming. The
following important pointer concepts should be clear to any C programmer –
Sr.No. Concept & Description
1 Pointer arithmetic: There are four arithmetic operators that can be used in pointers: ++,
--, +, -
2 Array of pointers: You can define arrays to hold a number of pointers.
3 Pointer to pointer: C allows you to have pointer on a pointer and so on.
4 Passing pointers to functions in C: Passing an argument by reference or by address enable
the passed argument to be changed in the calling function by the called function.
5 Return pointer from functions in C: C allows a function to return a pointer to the local
variable, static variable, and dynamically allocated memory as well.
C - Strings
Strings are actually one-dimensional array of characters terminated by a null character '0'. Thus a
null-terminated string contains the characters that comprise the string followed by a null.
The following declaration and initialization create a string consisting of the word "Hello". To hold
the null character at the end of the array, the size of the character array containing the string is one
more than the number of characters in the word "Hello."
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '0'};
If you follow the rule of array initialization then you can write the above statement as follows −
char greeting[] = "Hello";
Following is the memory presentation of the above defined string in C/C++ −
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Actually, you do not place the null character at the end of a string constant. The C compiler
automatically places the '0' at the end of the string when it initializes the array. Let us try to print
the above mentioned string −
#include <stdio.h>
int main ()
{
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '0'};
printf("Greeting message: %sn", greeting );
return 0;
}
When the above code is compiled and executed, it produces the following result −
Greeting message: Hello
C supports a wide range of functions that manipulate null-terminated strings –
Sr.No. Function & Purpose
1 strcpy(s1, s2);
Copies string s2 into string s1.
2 strcat(s1, s2);
Concatenates string s2 onto the end of string s1.
3 strlen(s1);
Returns the length of string s1.
4 strcmp(s1, s2);
Returns 0 if s1 and s2 are the same; less than 0 if s1<s2; greater than 0 if s1>s2.
5 strchr(s1, ch);
Returns a pointer to the first occurrence of character ch in string s1.
6 strstr(s1, s2);
Returns a pointer to the first occurrence of string s2 in string s1.
The following example uses some of the above-mentioned functions −
#include <stdio.h>
#include <string.h>
int main () {
char str1[12] = "Hello";
char str2[12] = "World";
char str3[12];
int len ;
/* copy str1 into str3 */
strcpy(str3, str1);
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printf("strcpy( str3, str1) : %sn", str3 );
/* concatenates str1 and str2 */
strcat( str1, str2);
printf("strcat( str1, str2): %sn", str1 );
/* total lenghth of str1 after concatenation */
len = strlen(str1);
printf("strlen(str1) : %dn", len );
return 0;
}
When the above code is compiled and executed, it produces the following result −
strcpy( str3, str1) : Hello
strcat( str1, str2): HelloWorld
strlen(str1) : 10
C - Structures
Arrays allow to define type of variables that can hold several data items of the same kind.
Similarly structure is another user defined data type available in C that allows to combine data
items of different kinds.
Structures are used to represent a record. Suppose you want to keep track of your books in a library.
You might want to track the following attributes about each book −
Title
Author
Subject
Book ID
Defining a Structure
To define a structure, you must use the struct statement. The struct statement defines a new data
type, with more than one member. The format of the struct statement is as follows −
struct [structure tag] {
member definition;
member definition;
...
member definition;
} [one or more structure variables];
The structure tag is optional and each member definition is a normal variable definition, such as
int i; or float f; or any other valid variable definition. At the end of the structure's definition, before
the final semicolon, you can specify one or more structure variables but it is optional.
Here is the way you would declare the Book structure −
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struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
} book;
Accessing Structure Members
To access any member of a structure, we use the member access operator (.). The member access
operator is coded as a period between the structure variable name and the structure member that
we wish to access. You would use the keyword struct to define variables of structure type. The
following example shows how to use a structure in a program −
#include <stdio.h>
#include <string.h>
struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
};
int main( ) {
struct Books Book1; /* Declare Book1 of type Book */
struct Books Book2; /* Declare Book2 of type Book */
/* book 1 specification */
strcpy( Book1.title, "C Programming");
strcpy( Book1.author, "Nuha Ali");
strcpy( Book1.subject, "C Programming Tutorial");
Book1.book_id = 6495407;
/* book 2 specification */
strcpy( Book2.title, "Telecom Billing");
strcpy( Book2.author, "Zara Ali");
strcpy( Book2.subject, "Telecom Billing Tutorial");
Book2.book_id = 6495700;
/* print Book1 info */
printf( "Book 1 title : %sn", Book1.title);
printf( "Book 1 author : %sn", Book1.author);
printf( "Book 1 subject : %sn", Book1.subject);
printf( "Book 1 book_id : %dn", Book1.book_id);
/* print Book2 info */
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Prof. K. Adisesha 33
printf( "Book 2 title : %sn", Book2.title);
printf( "Book 2 author : %sn", Book2.author);
printf( "Book 2 subject : %sn", Book2.subject);
printf( "Book 2 book_id : %dn", Book2.book_id);
return 0;
}
When the above code is compiled and executed, it produces the following result −
Book 1 title : C Programming
Book 1 author : Nuha Ali
Book 1 subject : C Programming Tutorial
Book 1 book_id : 6495407
Book 2 title : Telecom Billing
Book 2 author : Zara Ali
Book 2 subject : Telecom Billing Tutorial
Book 2 book_id : 6495700
C - Unions
A union is a special data type available in C that allows to store different data types in the same
memory location. You can define a union with many members, but only one member can contain
a value at any given time. Unions provide an efficient way of using the same memory location for
multiple-purpose.
Defining a Union
To define a union, you must use the union statement in the same way as you did while defining a
structure. The union statement defines a new data type with more than one member for your
program.
The format of the union statement is as follows −
union [union tag] {
member definition;
member definition;
...
member definition;
} [one or more union variables];
The union tag is optional and each member definition is a normal variable definition, such as int i;
or float f; or any other valid variable definition. At the end of the union's definition, before the
final semicolon, you can specify one or more union variables but it is optional. Here is the way
you would define a union type named Data having three members i, f, and str −
union Data {
int i;
float f;
char str[20];
} data;
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Prof. K. Adisesha 34
Now, a variable of Data type can store an integer, a floating-point number, or a string of characters.
It means a single variable, i.e., same memory location, can be used to store multiple types of data.
You can use any built-in or user defined data types inside a union based on your requirement.
The memory occupied by a union will be large enough to hold the largest member of the union.
For example, in the above example, Data type will occupy 20 bytes of memory space because this
is the maximum space which can be occupied by a character string. The following example
displays the total memory size occupied by the above union −
#include <stdio.h>
#include <string.h>
union Data {
int i;
float f;
char str[20];
};
int main( ) {
union Data data;
printf( "Memory size occupied by data : %dn", sizeof(data));
return 0;
}
When the above code is compiled and executed, it produces the following result −
Memory size occupied by data : 20
Accessing Union Members
To access any member of a union, we use the member access operator (.). The member access
operator is coded as a period between the union variable name and the union member that we wish
to access. You would use the keyword union to define variables of union type. The following
example shows how to use unions in a program −
#include <stdio.h>
#include <string.h>
union Data {
int i;
float f;
char str[20];
};
int main( ) {
union Data data;
data.i = 10;
data.f = 220.5;
strcpy( data.str, "C Programming");
printf( "data.i : %dn", data.i);
printf( "data.f : %fn", data.f);
printf( "data.str : %sn", data.str);
return 0;
}
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Prof. K. Adisesha 35
When the above code is compiled and executed, it produces the following result −
data.i : 1917853763
data.f : 4122360580327794860452759994368.000000
data.str : C Programming
Here, we can see that the values of i and f members of union got corrupted because the final value
assigned to the variable has occupied the memory location and this is the reason that the value
of str member is getting printed very well.
Now let's look into the same example once again where we will use one variable at a time which
is the main purpose of having unions −
#include <stdio.h>
#include <string.h>
union Data {
int i;
float f;
char str[20];
};
int main( ) {
union Data data;
data.i = 10;
printf( "data.i : %dn", data.i);
data.f = 220.5;
printf( "data.f : %fn", data.f);
strcpy( data.str, "C Programming");
printf( "data.str : %sn", data.str);
return 0;
}
When the above code is compiled and executed, it produces the following result −
data.i : 10
data.f : 220.500000