Passing an array to a function

An array isn't copied when you pass it. The parameter values is a pointer to the first box of scores in main, so the arrow points back into main's frame.

That's why double_all can change the caller's array, and why it needs the length passed separately: a pointer doesn't know how many boxes follow it.

#include <stdio.h>

void double_all(int values[], int n) {
    for (int i = 0; i < n; i++) {
        values[i] *= 2;
    }
}

int main(void) {
    int scores[3] = {4, 7, 9};
    double_all(scores, 3);
    printf("%d %d %d\n", scores[0], scores[1], scores[2]);
    return 0;
}

Output:

8 14 18

From the lesson: Arrays