What is the purpose of the design phase in program development?

Program development follows a defined sequence of phases: problem analysis, design, coding, testing, and documentation. Each phase produces a specific output that feeds into the next one.

The design phase comes after the problem has been analysed and before any code is written. Its purpose is to plan out how the program will work in a visual and logical form, mainly by creating a flow chart and an algorithm. A flow chart shows the sequence of steps using standard shapes and arrows, while an algorithm sets out those same steps as clear, ordered instructions in words or pseudocode. Together they act as a blueprint that the programmer follows when writing the actual source code.

Writing the source code, testing the program, and producing documentation all happen at later stages that build on this design; none of them can properly start until the design phase has mapped out the logic first.