The software development cycle fits within the system development life cycle, specifically within the development phase.
Be clear on what is needed and who will be using the program.
Be very clear on what the program must do and how it will be used.
Plan the program with IPOs, flowcharts and/or pseudocode
Determine inputs, processing, outputs (IPO eg)
eg What inputs are needed?, What processes will happen? What outputs are needed?
Make flowcharts, and/or algorithms and/or pseudocode.
Control structures; sequence, selection and loops are considered and used as wanted.
Code the program.
Use the pseudocode and a programming language of your choice.
Test (debug) the program to make sure it works as it is supposed to.
The program is evaluated to see if it does what it was designed to do.
When the program needs a software update, an improved version can be distributed.
Wikibooks here