Cambridge Syllabus Notes

11.3 Structured Programming 📚

Structured programming is all about breaking down a problem into smaller, manageable pieces called procedures and functions. Think of them as mini‑recipes that you can reuse throughout your code.

Terminology Overview

Procedure – A block of code that performs a task but does not return a value. It’s like a cooking step that doesn’t give you a final dish.
Function – Similar to a procedure but it returns a value. Think of it as a blender that gives you a smoothie.
Parameter – A variable listed in the procedure/function definition. It’s a placeholder for data you’ll supply later.
Argument – The actual value you pass to a parameter when you call the procedure/function.
Return Value – The result produced by a function and sent back to the caller.
Scope – The region of the program where a variable is visible. Local scope is inside a procedure/function; global scope is outside.

Procedures vs Functions

Both are called subroutines, but the key difference is the return value:

Type	Purpose	Example
Procedure	Performs an action, no value returned.	`void printWelcome()`
Function	Performs an action and returns a value.	`int add(int a, int b)`

Parameters & Arguments

When you define a procedure/function you specify parameters:

int multiply(int x, int y) { return x * y; }

When you call it you supply arguments:

int result = multiply(4, 5); // 4 and 5 are arguments

Return Values

A function uses the return keyword to give back a value. The type of the return value must match the function’s declared return type.

double average(int total, int count) {
    return (double)total / count;
}

If you forget return, the function may produce an error or an undefined value.

Scope & Lifetime

Variables declared inside a procedure/function are local and disappear once the block ends. Variables declared outside are global and exist throughout the program.

int globalScore = 0; // global

void updateScore(int points) {
    int localScore = points; // local
    globalScore += localScore;
}

Recursion (Optional)

A function that calls itself. Use it carefully to avoid infinite loops.

int factorial(int n) {
    if (n <= 1) return 1;
    return n * factorial(n - 1);
}

Exam Tips 📝

Identify whether the question asks for a procedure (no return) or a function (return value).
Use clear parameter names that describe the data (e.g., numStudents, averageScore).
Show the return statement explicitly if a value is required.
Remember to declare the correct return type (int, double, void, etc.).
Explain the difference between parameters and arguments in your answer.
When using recursion, state the base case and the recursive case.

Quick Quiz 🚀

Which of the following is a function?

void displayMessage()
int calculateSum(int a, int b)
string getName()

Answer: The ones that return a value (int, string) are functions; the one with void is a procedure.

Use the terminology associated with procedures and functions