What Is The Software Development Life Cycle?

This is the sequence of stages that you move through as you create a piece of software, a structured approach to its development, rather than just jumping in and starting coding straight away without any thought to what should be done in what order.

There are several different  software development life cycles, some are better suited to some types of projects than other.  One of the oldest and best known, but not actually the best in many cases, is the Waterfall model.  This assumes that  you will totally finish each stage before you do anything at all on the next stage.  At first glance this may make sense, but in practice it is flawed, because it also means you can't go back and alter bits you don't like, because you have agreed that that part is finished and complete!

It's steps are as follows

Feasibility study
Requirements gathering
System analysis
Design
Coding
Testing
Implementation
Maintenance

More modern lifecycles are iterative processes, and only require you to be about 80%  or so complete before you can move on to the next stage, returning to incomplete stages and improving them based on what was discovered when you moved on. And the return to revise is built into the system, it is not optional.