Software Development Life Cycle is a systematic approach to 
problem solving.  In most of the development organisations 
there is no systematic methodology for the dev. Generally, 
s/w development is considered as coding though coding forms 
a very small percentage of the  total development effort 
before starting the  coding one has to systematically 
approach the problem. To develop a s/w in a systematic way 
this S/w dev.life cycle is introduced.  convenient way of 
splitting this whole process  into five phrases those are 
1.requirements 2.desing 3.  coding 4. testing 5.  
maintainence.  
1. requirements phrase:  the purpose of this phrase is to 
define the requirements completely and it should be 
documented and agreed with customer before passing to next 
phase. one has to gather information abt the users, 
environment, security, performance, functions.  Business 
Analyst gather inf. from client by conducting meetings and 
discussions.
input: is inf.gathered from client 
process:requirement analysis 
output is S/w Requirements specification and Requirements 
Traceability Matrix.

2.  Design: this phase should provide the programmers 
necessary inf. to design and write s/w progrmmes to perform 
well defined tasks.  the design specidifcation should 
address the following areas  database designs, data 
conversions, user interface designs, External interfaces.  
Output of design phase is HLD and LLD, High level Doc. 
includes overall functionality of the appln. and Low level 
Doc. includes each individual module of the appln.  
input: will be SRS doc
Process: is  Design 
Output: is Detailed Design Doc.

3. Coding:  Design is converted into code while doing 
coding enough documentation has to be embedded in the code 
for easy understanding of the code by others.
input:  validated Design Doc, SRS
Process:  coding
Output is Source code

4. Testing: Soruce code is converted into an executiable 
code and various test inputs are given. For every test 
input the output is analyzed to chekc whether the programme 
is functioning directly
the output of the is stage is completely tested s/w which 
meets the requirements specifications.

input: SRS, Test Plan, Detailed design Doc., coding 
Process:  Testing
output is bug free s/w product

5. Maintainence:  Once all the above phrases are completed 
a s/w project enters the maintainence phase of the s/w life 
cycle.  Maintainence includes the following activities 
problem resolutions, interface modifications, functional 
expansion or performance improvement.

SDLC is a formal and logical steps taken to develop a 
software product.

steps involved are:
      Requirement gathering 
       Analysis
        Design
        Coding
        testing
        maintenance and implementaion