SDLC

Systems are created to solve problems.
One can think of the systems approach as an
organized way of dealing with a problem.
In this dynamic world, the subject System
Analysis and Design (SAD), mainly deals with
the software development activities.

•Define a system
•Explain the different phases of system
development life cycle
•Enumerate the components of system
analysis
•Explain the components of system designing

A collection of components that work
together to realize some objectives
forms a system.
Basically there are three major
components in every system, namely
input, processing and output.

In a system the different components are connected with each other
and they are interdependent. For example, human body represents
a complete natural system. We are also bound by many national
systems such as political system, economic system, educational system
and so forth. The objective of the system demands that some
output is produced as a result of processing the suitable inputs. A
well-designed system also includes an additional element referred
to as ‘control’ that provides a feedback to achieve desired objectives
of the system.

Preliminary system study is the first stage of
system development life cycle.
This is a brief investigation of the system under
consideration and gives a clear picture of what
actually the physical system is?

Initial system study involves the preparation of a
‘System Proposal’ which lists the Problem
Definition, Objectives of the Study, Terms of
reference for Study, Constraints, Expected benefits
of the new system, etc.

The system proposal is prepared by the System
Analyst (who studies the system) and places it
before the user management.
The management may accept the proposal and the
cycle proceeds to the next stage.
The management may also reject the proposal or
request some modifications in the proposal.

System study phase passes through the following
steps:
Problem identification and project initiation
Background analysis
Inference or findings (system proposal)

In case the system proposal is acceptable to the
management, the next phase is to examine the
feasibility of the system.
The feasibility study is basically the test of the
proposed system in the light of its workability,
meeting user’s requirements, effective use of
resources and of course, the cost effectiveness.

These are categorized as technical, operational,
economic and schedule feasibility. The main goal of
feasibility study is not to solve the problem but to
achieve the scope. In the process of feasibility
study, the cost and benefits are estimated with
greater accuracy to find the Return on Investment

This also defines the resources needed to complete the
detailed investigation.
The result is a feasibility report submitted to the
management. This may be accepted or accepted with
modifications or rejected.
The system cycle proceeds only if the management accepts
it.

The detailed investigation of the system is carried out in
accordance with the objectives of the proposed system.
This involves detailed study of various operations
performed by a system and their relationships within and
outside the system.

Using the following steps it becomes easy to draw the exact
boundary of the new system under consideration:
Keeping in view the problems and new requirements
Workout the pros and cons including new areas of the
system

All the data and the findings must be documented in the form of
detailed data flow diagrams (DFDs), data dictionary, logical data
structures.
The main points to be discussed in this stage are:
Specification of what the new system is to
accomplish based on the user requirements.

structures.
Functional hierarchy showing the functions to
be performed by the new system and their
relationship with each other.

structures.
List of attributes of the entities – these are the
data items which need to be held about each
entity (record)

System Analysis
Systems analysis is a process of collecting factual data, understand
the processes involved, identifying problems and recommending
feasible suggestions for improving the system functioning.
This involves studying the business processes, gathering operational
data, understand the information flow, finding out bottlenecks and
evolving solutions for overcoming the weaknesses of the system so
as to achieve the organizational goals.

System Analysis
The major objectives of systems analysis are to find answers for each
business process:
What is being done, How is it being done, Who is doing it, When is he
doing it, Why is it being done and How can it be improved?

Based on the user requirements and the
detailed analysis of the existing system, the
new system must be designed. This is the
phase of system designing.

It is the most crucial phase in the
developments of a system.
The logical system design arrived at as a
result of systems analysis is converted into
physical system design.

Normally, the design proceeds in two stages:
Preliminary or General Design
Structured or Detailed Design

Preliminary or General Design:
In the preliminary or general design, the features of the
new system are specified.
The costs of implementing these features and the benefits
to be derived are estimated.
If the project is still considered to be feasible, we move to
the detailed design stage.

Structured or Detailed Design:
In the detailed design stage, computer oriented work begins in
earnest.
At this stage, the design of the system becomes more structured.
Structure design is a blue print of a computer system solution to a
given problem having the same components and inter-relationships
among the same components as the original problem.

The system design involves:
i. Defining precisely the required system output
ii. Determining the data requirement for producing the output
iii. Determining the medium and format of files and databases
iv. Devising processing methods and use of software to produce output
v. Determine the methods of data capture and data input
vi. Designing Input forms
vii. Designing Codification Schemes
viii.Detailed manual procedures
ix. Documenting the Design

The system design needs to be implemented to
make it a workable system.
This demands the coding of design into computer
understandable language, i.e., programming
language.
This is also called the programming phase in
which the programmer converts the program
specifications into computer instructions, which
we refer to as programs.

Before actually implementing the new system
into operation, a test run of the system is done
for removing the bugs, if any.
It is an important phase of a successful system.
After codifying the whole programs of the
system, a test plan should be developed and run
on a given set of test data.
The output of the test run should match the
expected results.

Using the test data following test run are carried out:
White Box Testing / Program test:
When the programs have been coded, compiled and brought to working
conditions, they must be individually tested with the prepared test
data.
Any undesirable happening must be noted and debugged.

Using the test data following test run are carried out:
Black Box Testing / System Test:
At this stage the test is done on actual data. The complete system is
executed on the actual data.
At each stage of the execution, the results or output of the system is
analyzed. During the result analysis, it may be found that the outputs
are not matching the expected output of the system.
In such case, the errors in the particular programs are identified and
are fixed and further tested for the expected output.

After having the user acceptance of the new system developed, the
implementation phase begins. Implementation is the stage of a project
during which theory is turned into practice.
The major steps involved in this phase are:
Acquisition and Installation of Hardware and Software
Conversion
User Training
Documentation

During this phase, all the programs of the system are loaded onto the
user’s computer. After loading the system, training of the user starts.
Main topics of such type of training are:
How to execute the package
How to enter the data
How to process the data (processing details)
How to take out the reports

After the users are trained about the computerized system, working
has to shift from manual to computerized working. The process is
called ‘Changeover’.
The following strategies are followed for changeover of the system.
Direct Changeover:
This is the complete replacement of the old system by the new system.
It is a risky approach and requires comprehensive system testing and
training.

Parallel run:
In parallel run both the systems, i.e., computerized and manual, are
executed simultaneously for certain defined period.
The same data is processed by both the systems.
This strategy is less risky but more expensive because of the following:
Manual results can be compared with the results of the computerized
system.
The operational work is doubled.
Failure of the computerized system at the early stage does not affect
the working of the organization, because the manual system continues
to work, as it used to do.

Pilot run:
In this type of run, the new system is run with the data from one or
more of the previous periods for the whole or part of the system. The
results are compared with the old system results.
It is less expensive and risky than parallel run approach.
This strategy builds the confidence and the errors are traced easily
without affecting the operations.

The documentation of the system is also one of the most important
activity in the system development life cycle.
This ensures the continuity of the system.
There are generally two types of documentation prepared for any
system.
These are:
User or Operator Documentation
System Documentation

User documentation
Is a complete description of the system from the users point of view
detailing how to use or operate the system. It also includes the major
error messages likely to be encountered by the users.
System documentation
Contains the details of system design, programs, their coding, system
flow, data dictionary, process description, etc. This helps to understand
the system and permit changes to be made in the existing system to
satisfy new user needs.

Maintenance is necessary to eliminate errors in the system during its
working life and to tune the system to any variations in its working
environments. It also means the review of the system from time to
time.
The review of the system is done for:
knowing the full capabilities of the system
knowing the required changes or the additional requirements
studying the performance.
If a major change to a system is needed, a new project may have to be
set up to carry out the change. The new project will then proceed
through all the above life cycle phases.

SDLC

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to SDLC

Similar to SDLC (20)

More from nethisip13

More from nethisip13 (17)

Recently uploaded

Recently uploaded (20)

SDLC