The lexical analyzer is the first phase of a compiler. It takes source code as input and breaks it down into tokens by removing whitespace and comments. It identifies valid tokens by using patterns and regular expressions. The lexical analyzer generates a sequence of tokens that is passed to the subsequent syntax analysis phase. It helps locate errors by providing line and column numbers.
Lexical analysis is the process of converting a sequence of characters from a source program into a sequence of tokens. It involves reading the source program, scanning characters, grouping them into lexemes and producing tokens as output. The lexical analyzer also enters tokens into a symbol table, strips whitespace and comments, correlates error messages with line numbers, and expands macros. Lexical analysis produces tokens through scanning and tokenization and helps simplify compiler design and improve efficiency. It identifies tokens like keywords, constants, identifiers, numbers, operators and punctuation through patterns and deals with issues like lookahead and ambiguities.
The document discusses lexical analysis, which is the first phase of compilation. It involves reading the source code and grouping characters into meaningful sequences called lexemes. Each lexeme is mapped to a token that is passed to the subsequent parsing phase. Regular expressions are used to specify patterns for tokens. A lexical analyzer uses finite automata to recognize tokens based on these patterns. Lexical analyzers may also perform tasks like removing comments and whitespace from the source code.
Lexical Analysis, Tokens, Patterns, Lexemes, Example pattern, Stages of a Lexical Analyzer, Regular expressions to the lexical analysis, Implementation of Lexical Analyzer, Lexical analyzer: use as generator.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code as characters and converts them into tokens.
2. Syntax analysis checks token arrangements against the grammar to ensure syntactic correctness.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code optimization removes unnecessary code and improves efficiency.
6. Code generation translates the optimized intermediate code to machine language.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code and converts it to tokens.
2. Syntax analysis checks token arrangements against the grammar to validate syntax.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code is optimized in the intermediate representation.
6. Code generation produces machine code from the optimized intermediate code.
The document discusses the role and process of a lexical analyzer in compiler design. A lexical analyzer groups input characters into lexemes and produces a sequence of tokens as output for the syntactic analyzer. It strips out comments and whitespace, correlates line numbers with errors, and interacts with the symbol table. Lexical analysis improves compiler efficiency, portability, and allows for simpler parser design by separating lexical and syntactic analysis.
Lexical analysis is the process of converting a sequence of characters from a source program into a sequence of tokens. It involves reading the source program, scanning characters, grouping them into lexemes and producing tokens as output. The lexical analyzer also enters tokens into a symbol table, strips whitespace and comments, correlates error messages with line numbers, and expands macros. Lexical analysis produces tokens through scanning and tokenization and helps simplify compiler design and improve efficiency. It identifies tokens like keywords, constants, identifiers, numbers, operators and punctuation through patterns and deals with issues like lookahead and ambiguities.
The document discusses lexical analysis, which is the first phase of compilation. It involves reading the source code and grouping characters into meaningful sequences called lexemes. Each lexeme is mapped to a token that is passed to the subsequent parsing phase. Regular expressions are used to specify patterns for tokens. A lexical analyzer uses finite automata to recognize tokens based on these patterns. Lexical analyzers may also perform tasks like removing comments and whitespace from the source code.
Lexical Analysis, Tokens, Patterns, Lexemes, Example pattern, Stages of a Lexical Analyzer, Regular expressions to the lexical analysis, Implementation of Lexical Analyzer, Lexical analyzer: use as generator.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code as characters and converts them into tokens.
2. Syntax analysis checks token arrangements against the grammar to ensure syntactic correctness.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code optimization removes unnecessary code and improves efficiency.
6. Code generation translates the optimized intermediate code to machine language.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code and converts it to tokens.
2. Syntax analysis checks token arrangements against the grammar to validate syntax.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code is optimized in the intermediate representation.
6. Code generation produces machine code from the optimized intermediate code.
The document discusses the role and process of a lexical analyzer in compiler design. A lexical analyzer groups input characters into lexemes and produces a sequence of tokens as output for the syntactic analyzer. It strips out comments and whitespace, correlates line numbers with errors, and interacts with the symbol table. Lexical analysis improves compiler efficiency, portability, and allows for simpler parser design by separating lexical and syntactic analysis.
The document defines different phases of a compiler and describes Lexical Analysis in detail. It discusses:
1) A compiler converts a high-level language to machine language through front-end and back-end phases including Lexical Analysis, Syntax Analysis, Semantic Analysis, Intermediate Code Generation, Code Optimization and Code Generation.
2) Lexical Analysis scans the source code and groups characters into tokens by removing whitespace and comments. It identifies tokens like identifiers, keywords, operators etc.
3) A lexical analyzer generator like Lex takes a program written in the Lex language and produces a C program that acts as a lexical analyzer.
Tokens are the basic elements of a programming language like identifiers, keywords, operators, and punctuation. Patterns describe the rules for tokens and match lexical units or lexemes in the source code. For example, an identifier pattern may specify that it must start with a letter and can include alphanumeric characters. Lexemes are the specific instances of tokens in the code that are matched against patterns, like variable names. There are three main tokens - identifiers, operators, and punctuation - in the code example of count = count + temp.
This document discusses compiler construction and error handling. It describes the basic tasks of an error handler as detection, reporting, and recovery of errors encountered during compilation. Errors are classified and the document focuses on lexical analysis. The lexical analyzer takes source code as character streams and breaks it into tokens based on predefined patterns and grammar rules. It generates errors for invalid tokens and works closely with the syntax analyzer by passing tokenized data.
This document discusses compiler construction and error handling. It describes the basic tasks of an error handler as detection, reporting, and recovery of errors encountered during compilation. Errors are classified and the document focuses on lexical analysis. The lexical analyzer takes source code as character streams and breaks it into tokens based on predefined patterns and grammar rules. It generates errors for invalid tokens and works closely with the syntax analyzer by passing tokenized data.
Using Static Analysis in Program DevelopmentPVS-Studio
The document discusses static analysis, which allows checking program code before execution. It describes the static analysis process, which involves lexing, parsing, and abstract syntax tree (AST) creation. Various static analysis techniques are then performed on the AST, including AST walker analysis, data flow analysis, and path-sensitive data flow analysis. The document provides examples of how ASTs represent code and are used in static analysis.
The document discusses the role and implementation of a lexical analyzer. It can be summarized as:
1. A lexical analyzer scans source code, groups characters into lexemes, and produces tokens which it returns to the parser upon request. It handles tasks like removing whitespace and expanding macros.
2. It implements buffering techniques to efficiently scan large inputs and uses transition diagrams to represent patterns for matching tokens.
3. Regular expressions are used to specify patterns for tokens, and flex is a common language for implementing lexical analyzers based on these specifications.
The document discusses the differences between compilers and interpreters. It states that a compiler translates an entire program into machine code in one pass, while an interpreter translates and executes code line by line. A compiler is generally faster than an interpreter, but is more complex. The document also provides an overview of the lexical analysis phase of compiling, including how it breaks source code into tokens, creates a symbol table, and identifies patterns in lexemes.
Token, Pattern and Lexeme defines some key concepts in lexical analysis:
Tokens are valid sequences of characters that can be identified as keywords, constants, identifiers, numbers, operators or punctuation. A lexeme is the sequence of characters that matches a token pattern. Patterns are defined by regular expressions or grammar rules to identify lexemes as specific tokens. The lexical analyzer collects attributes like values for number tokens and symbol table entries for identifiers and passes the tokens and attributes to the parser. Lexical errors occur if a character sequence cannot be scanned as a valid token. Error recovery strategies include deleting or inserting characters to allow tokenization to continue.
The document provides an overview of compilers and interpreters. It discusses that a compiler translates source code into machine code that can be executed, while an interpreter executes source code directly without compilation. The document then covers the typical phases of a compiler in more detail, including the front-end (lexical analysis, syntax analysis, semantic analysis), middle-end/optimizer, and back-end (code generation). It also discusses interpreters, intermediate code representation, symbol tables, and compiler construction tools.
The document discusses the lexical analysis phase of a compiler. In lexical analysis, the source code is divided into tokens. Common token types include keywords, identifiers, and special symbols. Lexical analyzers perform pattern matching and techniques used for lexical analysis can also be applied to other areas like query languages. Lex is a tool that can generate an automaton recognizer for regular expressions to specify lexical analyzers. The role of a lexical analyzer is to read input characters and produce a sequence of tokens for the parser to use in syntax analysis.
This document provides an introduction to compilers and their construction. It defines a compiler as a program that translates a source program into target machine code. The compilation process involves several phases including lexical analysis, syntax analysis, semantic analysis, code optimization, and code generation. An interpreter directly executes source code without compilation. The document also discusses compiler tools and intermediate representations used in the compilation process.
This document provides information about the CS213 Programming Languages Concepts course taught by Prof. Taymoor Mohamed Nazmy in the computer science department at Ain Shams University in Cairo, Egypt. It describes the syntax and semantics of programming languages, discusses different programming language paradigms like imperative, functional, and object-oriented, and explains concepts like lexical analysis, parsing, semantic analysis, symbol tables, intermediate code generation, optimization, and code generation which are parts of the compiler design process.
The document discusses the role and implementation of a lexical analyzer in compilers. A lexical analyzer is the first phase of a compiler that reads source code characters and generates a sequence of tokens. It groups characters into lexemes and determines the tokens based on patterns. A lexical analyzer may need to perform lookahead to unambiguously determine tokens. It associates attributes with tokens, such as symbol table entries for identifiers. The lexical analyzer and parser interact through a producer-consumer relationship using a token buffer.
In this presentation following topics have been told.
1. What are translators?
2. Different types of translators.
3. working of compiler and interpreter.
4. phases of compiler.
Lexical analysis is the first phase of compilation. It reads source code characters and divides them into tokens by recognizing patterns using finite automata. It separates tokens, inserts them into a symbol table, and eliminates unnecessary characters. Tokens are passed to the parser along with line numbers for error handling. An input buffer is used to improve efficiency by reading source code in blocks into memory rather than character-by-character from secondary storage. Lexical analysis groups character sequences into lexemes, which are then classified as tokens based on patterns.
The document discusses syntax analysis in compiler design. It defines syntax analysis as the process of analyzing a string of symbols according to the rules of a formal grammar. This involves checking the syntax against a context-free grammar, which is more powerful than regular expressions and can check balancing of tokens. The output of syntax analysis is a parse tree. It separates lexical analysis and parsing for simplicity and efficiency. Lexical analysis breaks the source code into tokens, while parsing analyzes token streams against production rules to detect errors and generate the parse tree.
The lexical analyzer takes a string of characters as input and divides it into tokens, filtering out whitespace and comments. It interacts with the parser by returning tokens one by one when called. The lexical analyzer simplifies the work of the parser by eliminating unwanted tokens and errors are correlated with line numbers. It is sometimes divided into a scanning and analysis process. In comparison, the parser performs syntax analysis by creating an abstract representation and symbol table entries while the lexical analyzer identifies tokens and inserts them into the symbol table.
The document discusses the roles of compilers and interpreters. It explains that a compiler translates an entire program into machine code in one pass, while an interpreter translates and executes code line-by-line. The document also covers the basics of lexical analysis, including how it breaks source code into tokens by removing whitespace and comments. It provides an example of tokens identified in a code snippet and discusses how the lexical analyzer works with the symbol table and syntax analyzer.
8+8+8 Rule Of Time Management For Better ProductivityRuchiRathor2
This is a great way to be more productive but a few things to
Keep in mind:
- The 8+8+8 rule offers a general guideline. You may need to adjust the schedule depending on your individual needs and commitments.
- Some days may require more work or less sleep, demanding flexibility in your approach.
- The key is to be mindful of your time allocation and strive for a healthy balance across the three categories.
The document defines different phases of a compiler and describes Lexical Analysis in detail. It discusses:
1) A compiler converts a high-level language to machine language through front-end and back-end phases including Lexical Analysis, Syntax Analysis, Semantic Analysis, Intermediate Code Generation, Code Optimization and Code Generation.
2) Lexical Analysis scans the source code and groups characters into tokens by removing whitespace and comments. It identifies tokens like identifiers, keywords, operators etc.
3) A lexical analyzer generator like Lex takes a program written in the Lex language and produces a C program that acts as a lexical analyzer.
Tokens are the basic elements of a programming language like identifiers, keywords, operators, and punctuation. Patterns describe the rules for tokens and match lexical units or lexemes in the source code. For example, an identifier pattern may specify that it must start with a letter and can include alphanumeric characters. Lexemes are the specific instances of tokens in the code that are matched against patterns, like variable names. There are three main tokens - identifiers, operators, and punctuation - in the code example of count = count + temp.
This document discusses compiler construction and error handling. It describes the basic tasks of an error handler as detection, reporting, and recovery of errors encountered during compilation. Errors are classified and the document focuses on lexical analysis. The lexical analyzer takes source code as character streams and breaks it into tokens based on predefined patterns and grammar rules. It generates errors for invalid tokens and works closely with the syntax analyzer by passing tokenized data.
This document discusses compiler construction and error handling. It describes the basic tasks of an error handler as detection, reporting, and recovery of errors encountered during compilation. Errors are classified and the document focuses on lexical analysis. The lexical analyzer takes source code as character streams and breaks it into tokens based on predefined patterns and grammar rules. It generates errors for invalid tokens and works closely with the syntax analyzer by passing tokenized data.
Using Static Analysis in Program DevelopmentPVS-Studio
The document discusses static analysis, which allows checking program code before execution. It describes the static analysis process, which involves lexing, parsing, and abstract syntax tree (AST) creation. Various static analysis techniques are then performed on the AST, including AST walker analysis, data flow analysis, and path-sensitive data flow analysis. The document provides examples of how ASTs represent code and are used in static analysis.
The document discusses the role and implementation of a lexical analyzer. It can be summarized as:
1. A lexical analyzer scans source code, groups characters into lexemes, and produces tokens which it returns to the parser upon request. It handles tasks like removing whitespace and expanding macros.
2. It implements buffering techniques to efficiently scan large inputs and uses transition diagrams to represent patterns for matching tokens.
3. Regular expressions are used to specify patterns for tokens, and flex is a common language for implementing lexical analyzers based on these specifications.
The document discusses the differences between compilers and interpreters. It states that a compiler translates an entire program into machine code in one pass, while an interpreter translates and executes code line by line. A compiler is generally faster than an interpreter, but is more complex. The document also provides an overview of the lexical analysis phase of compiling, including how it breaks source code into tokens, creates a symbol table, and identifies patterns in lexemes.
Token, Pattern and Lexeme defines some key concepts in lexical analysis:
Tokens are valid sequences of characters that can be identified as keywords, constants, identifiers, numbers, operators or punctuation. A lexeme is the sequence of characters that matches a token pattern. Patterns are defined by regular expressions or grammar rules to identify lexemes as specific tokens. The lexical analyzer collects attributes like values for number tokens and symbol table entries for identifiers and passes the tokens and attributes to the parser. Lexical errors occur if a character sequence cannot be scanned as a valid token. Error recovery strategies include deleting or inserting characters to allow tokenization to continue.
The document provides an overview of compilers and interpreters. It discusses that a compiler translates source code into machine code that can be executed, while an interpreter executes source code directly without compilation. The document then covers the typical phases of a compiler in more detail, including the front-end (lexical analysis, syntax analysis, semantic analysis), middle-end/optimizer, and back-end (code generation). It also discusses interpreters, intermediate code representation, symbol tables, and compiler construction tools.
The document discusses the lexical analysis phase of a compiler. In lexical analysis, the source code is divided into tokens. Common token types include keywords, identifiers, and special symbols. Lexical analyzers perform pattern matching and techniques used for lexical analysis can also be applied to other areas like query languages. Lex is a tool that can generate an automaton recognizer for regular expressions to specify lexical analyzers. The role of a lexical analyzer is to read input characters and produce a sequence of tokens for the parser to use in syntax analysis.
This document provides an introduction to compilers and their construction. It defines a compiler as a program that translates a source program into target machine code. The compilation process involves several phases including lexical analysis, syntax analysis, semantic analysis, code optimization, and code generation. An interpreter directly executes source code without compilation. The document also discusses compiler tools and intermediate representations used in the compilation process.
This document provides information about the CS213 Programming Languages Concepts course taught by Prof. Taymoor Mohamed Nazmy in the computer science department at Ain Shams University in Cairo, Egypt. It describes the syntax and semantics of programming languages, discusses different programming language paradigms like imperative, functional, and object-oriented, and explains concepts like lexical analysis, parsing, semantic analysis, symbol tables, intermediate code generation, optimization, and code generation which are parts of the compiler design process.
The document discusses the role and implementation of a lexical analyzer in compilers. A lexical analyzer is the first phase of a compiler that reads source code characters and generates a sequence of tokens. It groups characters into lexemes and determines the tokens based on patterns. A lexical analyzer may need to perform lookahead to unambiguously determine tokens. It associates attributes with tokens, such as symbol table entries for identifiers. The lexical analyzer and parser interact through a producer-consumer relationship using a token buffer.
In this presentation following topics have been told.
1. What are translators?
2. Different types of translators.
3. working of compiler and interpreter.
4. phases of compiler.
Lexical analysis is the first phase of compilation. It reads source code characters and divides them into tokens by recognizing patterns using finite automata. It separates tokens, inserts them into a symbol table, and eliminates unnecessary characters. Tokens are passed to the parser along with line numbers for error handling. An input buffer is used to improve efficiency by reading source code in blocks into memory rather than character-by-character from secondary storage. Lexical analysis groups character sequences into lexemes, which are then classified as tokens based on patterns.
The document discusses syntax analysis in compiler design. It defines syntax analysis as the process of analyzing a string of symbols according to the rules of a formal grammar. This involves checking the syntax against a context-free grammar, which is more powerful than regular expressions and can check balancing of tokens. The output of syntax analysis is a parse tree. It separates lexical analysis and parsing for simplicity and efficiency. Lexical analysis breaks the source code into tokens, while parsing analyzes token streams against production rules to detect errors and generate the parse tree.
The lexical analyzer takes a string of characters as input and divides it into tokens, filtering out whitespace and comments. It interacts with the parser by returning tokens one by one when called. The lexical analyzer simplifies the work of the parser by eliminating unwanted tokens and errors are correlated with line numbers. It is sometimes divided into a scanning and analysis process. In comparison, the parser performs syntax analysis by creating an abstract representation and symbol table entries while the lexical analyzer identifies tokens and inserts them into the symbol table.
The document discusses the roles of compilers and interpreters. It explains that a compiler translates an entire program into machine code in one pass, while an interpreter translates and executes code line-by-line. The document also covers the basics of lexical analysis, including how it breaks source code into tokens by removing whitespace and comments. It provides an example of tokens identified in a code snippet and discusses how the lexical analyzer works with the symbol table and syntax analyzer.
8+8+8 Rule Of Time Management For Better ProductivityRuchiRathor2
This is a great way to be more productive but a few things to
Keep in mind:
- The 8+8+8 rule offers a general guideline. You may need to adjust the schedule depending on your individual needs and commitments.
- Some days may require more work or less sleep, demanding flexibility in your approach.
- The key is to be mindful of your time allocation and strive for a healthy balance across the three categories.
How to Create User Notification in Odoo 17Celine George
This slide will represent how to create user notification in Odoo 17. Odoo allows us to create and send custom notifications on some events or actions. We have different types of notification such as sticky notification, rainbow man effect, alert and raise exception warning or validation.
The Science of Learning: implications for modern teachingDerek Wenmoth
Keynote presentation to the Educational Leaders hui Kōkiritia Marautanga held in Auckland on 26 June 2024. Provides a high level overview of the history and development of the science of learning, and implications for the design of learning in our modern schools and classrooms.
Creativity for Innovation and SpeechmakingMattVassar1
Tapping into the creative side of your brain to come up with truly innovative approaches. These strategies are based on original research from Stanford University lecturer Matt Vassar, where he discusses how you can use them to come up with truly innovative solutions, regardless of whether you're using to come up with a creative and memorable angle for a business pitch--or if you're coming up with business or technical innovations.
Decolonizing Universal Design for LearningFrederic Fovet
UDL has gained in popularity over the last decade both in the K-12 and the post-secondary sectors. The usefulness of UDL to create inclusive learning experiences for the full array of diverse learners has been well documented in the literature, and there is now increasing scholarship examining the process of integrating UDL strategically across organisations. One concern, however, remains under-reported and under-researched. Much of the scholarship on UDL ironically remains while and Eurocentric. Even if UDL, as a discourse, considers the decolonization of the curriculum, it is abundantly clear that the research and advocacy related to UDL originates almost exclusively from the Global North and from a Euro-Caucasian authorship. It is argued that it is high time for the way UDL has been monopolized by Global North scholars and practitioners to be challenged. Voices discussing and framing UDL, from the Global South and Indigenous communities, must be amplified and showcased in order to rectify this glaring imbalance and contradiction.
This session represents an opportunity for the author to reflect on a volume he has just finished editing entitled Decolonizing UDL and to highlight and share insights into the key innovations, promising practices, and calls for change, originating from the Global South and Indigenous Communities, that have woven the canvas of this book. The session seeks to create a space for critical dialogue, for the challenging of existing power dynamics within the UDL scholarship, and for the emergence of transformative voices from underrepresented communities. The workshop will use the UDL principles scrupulously to engage participants in diverse ways (challenging single story approaches to the narrative that surrounds UDL implementation) , as well as offer multiple means of action and expression for them to gain ownership over the key themes and concerns of the session (by encouraging a broad range of interventions, contributions, and stances).
2. • Lexical analysis is the first phase of a compiler. It takes modified source code from
language preprocessors that are written in the form of sentences. The lexical analyzer
breaks these syntaxes into a series of tokens, by removing any whitespace or comments
in the source code.
• Lexical Analysis is the first phase of the compiler also known as a scanner. It converts
the High level input program into a sequence of Tokens.
• If the lexical analyzer finds a token invalid, it generates an error. The lexical
analyzer works closely with the syntax analyzer. It reads character streams from the
source code, checks for legal tokens, and passes the data to the syntax analyzer
when it demands.
• Tokens
Lexemes are said to be a sequence of characters (alphanumeric) in a token. There
are some predefined rules for every lexeme to be identified as a valid token. These
rules are defined by grammar rules, by means of a pattern. A pattern explains what
can be a token, and these patterns are defined by means of regular expressions.
3. •Lexical Analysis can be implemented with the Deterministic finite Automata.
• The output is a sequence of tokens that is sent to the parser for syntax analysis
4. • What is a token?
A lexical token is a sequence of characters that can be treated as a unit in the grammar
of the programming languages.
Example of tokens:
• Type token (id, number, real, . . . )
• Punctuation tokens (IF, void, return, . . . )
• Alphabetic tokens (keywords)
Keywords; Examples- for, while, if etc.
Identifier; Examples-Variable name, function name, etc.
Operators; Examples '+', '++', '-' etc.
Separators; Examples ',' ';' etc
Example of Non-Tokens:
•Comments, preprocessor directive, macros, blanks, tabs, newline, etc.
5. Lexeme: The sequence of characters matched by a pattern to form
the corresponding token or a sequence of input characters that comprises a single token is
called a lexeme.
eg- “float”, “abs_zero_Kelvin”, “=”, “-”, “273”, “;”
How Lexical Analyzer functions
1. Tokenization i.e. Dividing the program into valid tokens.
2. Remove white space characters.
3. Remove comments.
4. It also provides help in generating error messages by providing row numbers and column
numbers.
6. Suppose we pass a statement through lexical analyzer –
a = b + c ; It will generate token sequence like this:
id=id+id; Where each id refers to it’s variable in the symbol table referencing all details
For example, consider the program
int main()
{ // 2 variables
int a, b; a = 10;
return 0;
}
All the valid tokens are:
'int’ 'main’ '(‘ ')’ '{‘ 'int’ 'a' ‘, ' 'b’ ';' ‘ a' '=‘ ‘ 10’ ';’
'return’ '0' ';’ '}'
Above are the valid tokens.
You can observe that we have omitted comments.
7. Exercise 1:
Count number of tokens :
int main()
{
int a = 10, b = 20;
printf("sum is :%d", a + b );
return 0;
}
8. Answer: Total number of token: 27.
Exercise 2:
Count number of tokens :
int max(int i);
•Lexical analyzer first read int and finds it to be valid and accepts as token
•max is read by it and found to be a valid function name after reading (
• int is also a token , then again i as another token and finally ;
Answer: Total number of tokens 7
9. Basic Terminologies
What’s a lexeme?
A lexeme is a sequence of characters that are included in the source program according to the
matching pattern of a token. It is nothing but an instance of a token.
What’s a token?
Tokens in compiler design are the sequence of characters which represents a unit of
information in the source program.
What is Pattern?
A pattern is a description which is used by the token. In the case of a keyword which uses
as a token, the pattern is a sequence of characters.
10. Roles of the Lexical analyzer:
Lexical analyzer performs below given tasks:
• Helps to identify token into the symbol table
• Removes white spaces and comments from the source program
• Correlates error messages with the source program
• Helps you to expands the macros if it is found in the source program
• Read input characters from the source program
Lexical Errors
A character sequence which is not possible to scan into any valid token is
a lexical error.
11. • Lexical errors are not very common, but it should be managed by a scanner
• Misspelling of identifiers, operators, keyword are considered as lexical errors
• Generally, a lexical error is caused by the appearance of some illegal character, mostly
at the beginning of a token.
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