1.3 Program Design and Development

The Development Process

Programs are built through an iterative and incremental process: plan, write code, test, and refine repeatedly. Programmers use incremental development — building and testing small pieces before adding more — to catch errors early and manage complexity. This approach makes it easier to isolate bugs and improve a program over time.

Collaboration and Documentation

Effective programs often result from collaboration, where teams share ideas, divide tasks, and use pair programming or code reviews to improve quality. Comments (program documentation) explain what code does, making it easier for others — and yourself — to read, debug, and maintain the program. Good documentation supports collaboration across a team.

Algorithms and Debugging

An algorithm is a finite set of instructions to accomplish a task or solve a problem. When programs don't work as intended, programmers use debugging — locating and fixing errors — often with test cases designed to check specific input/output behavior, including edge cases that reveal hidden bugs.

Key terms

Incremental development

Building and testing a program in small pieces before adding more, to catch errors early.

Algorithm

A finite set of instructions used to accomplish a task or solve a problem.

Debugging

The process of locating and fixing errors (bugs) in a program.

Test case

A specific set of inputs and expected outputs used to check whether a program works correctly, including edge cases.

Program documentation

Comments and notes within code that explain its purpose and function, aiding readability and collaboration.

Try an AP-style question

What is an iterative development process?

1. Writing all code once without testing
2. Testing only on the final day
3. Repeating design, testing, and refining cycles
4. Designing only after the program is done