Demo: Pass an Address to a Function

Fix a stock count through its address

Passing an address copies it to the function parameter without copying the pointed-to integer.

An inventory correction needs to change the count held in main. Passing an int alone would give the function a copy. Passing &stock copies its address instead, and *item then refers to the original stock. The pointer parameter is a copy, but the integer it points to is shared for the duration of the call.

#include <stdio.h>

void correct_count(int *item) {
    *item += 4;
}

int main(void) {
    int stock = 7;
    correct_count(&stock);
    printf("Stock: %d\n", stock);
    return 0;
}

Trace the call: stock is 7, item points to it, *item becomes 11, then main prints 11. Change 4 to 2 and predict the output. In the exercise, you will use two addresses to exchange counts instead of adding to one.

Demo: Pass an Address to a Function

Fix a stock count through its address

#include <stdio.h>

void correct_count(int *item) {
    *item += 4;
}

int main(void) {
    int stock = 7;
    correct_count(&stock);
    printf("Stock: %d\n", stock);
    return 0;
}