Developing Procedures Chapter Notes | AP Computer Science Principles - Grade 9 PDF Download

Introduction

Developing procedures is a core concept in AP Computer Science Principles, enabling programmers to break down complex tasks into simpler, reusable parts. This chapter explores procedural abstraction, a method that allows procedures to be used without understanding their inner workings. It discusses how procedures enhance code modularity, readability, and reusability, using examples like a summing function. By learning to develop procedures, programmers can create more organized and maintainable programs.

Procedural Abstraction

• Procedural abstraction is a type of abstraction that lets you use procedures without knowing how they work.
  • Example: The print() function is a built-in procedure used without understanding its internal code.
• Procedures solve big problems by breaking them into smaller sub-problems.
  • Example: A choose-your-own-adventure game uses procedures to handle path choices, display options, and track player progress.
• Each sub-problem is solved with a procedure, and these are combined to create the full program.

Modularity

• Modularity is dividing a program into separate sub-programs or procedures.
• It makes programs easier to manage and understand.
• Procedures improve code readability by reducing repetition.
• Example: Instead of repeating code to add numbers multiple times, use a procedure:
  • Without procedure: Write first_number = 7; second_number = 5; sum_value = first_number + second_number; print(sum_value) for each pair.
  • With procedure: def summing_machine(first_number, second_number): sum_value = first_number + second_number; print(sum_value)
  • Call it: summing_machine(5, 7); summing_machine(8, 2); summing_machine(9, 3).
  • The procedure version is shorter and clearer, especially in large programs.

Reusability and Flexibility

• Procedures can be reused across different parts of a program.
• Parameters make procedures flexible by representing general data types, like numbers or strings.
• Example: summing_machine can add any two numbers, not specific ones, due to its general parameters.
• Procedural abstraction allows changes to a procedure without affecting the whole program, as long as the procedure’s behavior remains the same.
• Edits to a procedure apply everywhere it’s called, saving time.

Return Statement

• A return statement in a procedure sends a value back to the code that called it.
• It can appear anywhere in the procedure and stops the procedure immediately.
• The returned value of the expression specified in the statement can be used in the program parts.

Key Terms

• Procedural Abstraction: A technique for breaking down complex tasks into smaller, manageable procedures, improving code organization and maintainability.
• Return Statement: A statement that specifies the value a function returns to its caller, enabling data to be passed back from the function.