Role of Function in Programming

A function is a self-contained block of code that performs a specific task and can be reused multiple times in a program.

Role of Function in Programming

• Modularity — Breaks a large program into smaller, manageable parts
• Reusability — Same function can be called multiple times without rewriting code
• Readability — Makes program easier to understand and maintain
• Debugging — Errors can be isolated and fixed within individual functions
• Abstraction — Hides complex logic and provides a simple interface

Function Declaration (Prototype)

Tells the compiler about the function's name, return type, and parameters before it is used.

return_type function_name(parameter_list);

Example: int add(int a, int b);

Function Definition

Contains the actual body of the function with the code to be executed.

int add(int a, int b) {
    return a + b;
}

Function Call

Invokes the function to execute its code by passing actual arguments.

int result = add(5, 3);

Conclusion: Functions make programs organized, reusable, and easier to debug by dividing complex problems into smaller sub-problems.

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Program to Find Factorial of 'n' Using Recursive Function [5 marks]

A recursive function is a function that calls itself repeatedly until a base condition is met.

#include <stdio.h>

int factorial(int n) {
    if (n == 0 || n == 1)
        return 1;           // Base condition
    else
        return n * factorial(n - 1);  // Recursive call
}

int main() {
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);
    printf("Factorial of %d = %d", n, factorial(n));
    return 0;
}

How It Works (for n = 5):

• factorial(5) = 5 × factorial(4)
• factorial(4) = 4 × factorial(3)
• factorial(3) = 3 × factorial(2)
• factorial(2) = 2 × factorial(1)
• factorial(1) = 1 (Base condition reached)

Final Result: 5 × 4 × 3 × 2 × 1 = 120

Conclusion: Recursion simplifies problems like factorial by breaking them into smaller identical sub-problems until the base case is reached.