Write a program to demonstrate the call by value and the call by reference concepts in c.

 #include <stdio.h>

// Call by Value - receives copy of arguments

void swapByValue(int a, int b) {

    int temp;

    printf("\nInside swapByValue (before swap):\n");

    printf("a = %d, b = %d\n", a, b);

    

    temp = a;

    a = b;

    b = temp;

    

    printf("Inside swapByValue (after swap):\n");

    printf("a = %d, b = %d\n", a, b);

}

// Call by Reference - receives addresses of arguments

void swapByReference(int *a, int *b) {

    int temp;

    printf("\nInside swapByReference (before swap):\n");

    printf("*a = %d, *b = %d\n", *a, *b);

    

    temp = *a;

    *a = *b;

    *b = temp;

    

    printf("Inside swapByReference (after swap):\n");

    printf("*a = %d, *b = %d\n", *a, *b);

}

// Call by Value - modifying the parameter

void incrementByValue(int num) {

    printf("\nInside incrementByValue (before):\n");

    printf("num = %d\n", num);

    

    num = num + 10;

    

    printf("Inside incrementByValue (after):\n");

    printf("num = %d\n", num);

}

// Call by Reference - modifying through pointer

void incrementByReference(int *num) {

    printf("\nInside incrementByReference (before):\n");

    printf("*num = %d\n", *num);

    

    *num = *num + 10;

    

    printf("Inside incrementByReference (after):\n");

    printf("*num = %d\n", *num);

}

// Call by Value - calculating area (returns value)

int calculateArea(int length, int width) {

    return length * width;

}

// Call by Reference - calculating area (modifies through pointer)

void calculateAreaByRef(int length, int width, int *area) {

    *area = length * width;

}

int main() {

    printf("========== CALL BY VALUE vs CALL BY REFERENCE ==========\n");

    

    // Example 1: Swap using Call by Value

    printf("\n***** EXAMPLE 1: SWAP FUNCTION *****\n");

    int x = 10, y = 20;

    

    printf("\n--- Call by Value ---");

    printf("\nBefore calling swapByValue: x = %d, y = %d\n", x, y);

    swapByValue(x, y);

    printf("After calling swapByValue: x = %d, y = %d\n", x, y);

    printf("Notice: Original values NOT changed!\n");

    

    printf("\n--- Call by Reference ---");

    printf("\nBefore calling swapByReference: x = %d, y = %d\n", x, y);

    swapByReference(&x, &y);

    printf("After calling swapByReference: x = %d, y = %d\n", x, y);

    printf("Notice: Original values ARE changed!\n");

    

    // Example 2: Increment using both methods

    printf("\n\n***** EXAMPLE 2: INCREMENT FUNCTION *****\n");

    int num1 = 50, num2 = 50;

    

    printf("\n--- Call by Value ---");

    printf("\nBefore calling incrementByValue: num1 = %d\n", num1);

    incrementByValue(num1);

    printf("After calling incrementByValue: num1 = %d\n", num1);

    

    printf("\n--- Call by Reference ---");

    printf("\nBefore calling incrementByReference: num2 = %d\n", num2);

    incrementByReference(&num2);

    printf("After calling incrementByReference: num2 = %d\n", num2);

    

    // Example 3: Calculate area

    printf("\n\n***** EXAMPLE 3: CALCULATE AREA *****\n");

    int length = 5, width = 10;

    

    printf("\n--- Call by Value (return value) ---\n");

    int area1 = calculateArea(length, width);

    printf("Area = %d\n", area1);

    

    printf("\n--- Call by Reference (modify through pointer) ---\n");

    int area2;

    calculateAreaByRef(length, width, &area2);

    printf("Area = %d\n", area2);

    

    // Summary

    printf("\n\n========== SUMMARY ==========\n");

    printf("CALL BY VALUE:\n");

    printf("  - Passes copy of variable\n");

    printf("  - Changes inside function don't affect original\n");

    printf("  - Safer but uses more memory\n\n");

    

    printf("CALL BY REFERENCE:\n");

    printf("  - Passes address of variable (using pointers)\n");

    printf("  - Changes inside function affect original\n");

    printf("  - More efficient for large data\n");

    printf("  - Use & to pass address, * to access value\n");

    

    return 0;

}