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CS156 Reference: Passing Arguments by Reference

Passing by Reference instead of by value

• If we want a function to affect the variables in the calling function, we can send the address of the variables.
• This is passing by reference instead of passing by value
• Remember the use of the & for scanf, to reference the address of a variable
• &num means “the address of num”

Passing by Reference, not by value

/* Pass by value */
void doStuff(int val) {
    val = 3;
}
int main( ) {
    int x = 5;
    doStuff(x);
    printf("After, x=%d\n", x);
    return 0;
}

After, x=5

/* Pass by reference */
void doStuff(int *val) {
    *val = 3;
}
int main( ) {
    int x = 5;
    doStuff(&x);
    printf("After, x=%d\n", x);
    return 0;
}

After, x=3