Pointers as Function Arguments

You can pass pointers as arguments to functions.

• This allows the function to directly access and modify the variable whose address is passed.
• Passing pointers enables call-by-reference behavior in C.

Why Use?

• To modify the actual value of a variable inside a function.
• To pass large arrays or data efficiently without copying.
• To return multiple values using pointers.

Example:

#include <stdio.h>

// Function to swap two integers using pointers
void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

int main() {
    int x = 10, y = 20;
    printf("Before swap: x = %d, y = %d\n", x, y);

    swap(&x, &y);  // Passing addresses of x and y

    printf("After swap: x = %d, y = %d\n", x, y);
    return 0;
}

Function Returning Pointers

Functions can return pointers.

• This is useful when the function needs to return the address of a variable or array.

• Important: The pointer returned must point to valid memory (not to a local variable inside the function, which goes out of scope).

Example: Returning pointer to array

#include <stdio.h>

int* getArray() {
    static int arr[3] = {1, 2, 3};  // static so it persists after function ends
    return arr;                      // return address of first element
}

int main() {
    int *ptr = getArray();

    for (int i = 0; i < 3; i++) {
        printf("%d ", ptr[i]);
    }
    printf("\n");

    return 0;
}