Why function will not change variable?

Question

In this code I seem to get zero, I\'m not too familiar with as to why I can\'t change the variable length with the function I created. Any help could be useful.

Answer 1

You're not storing the return value. Change:

get_length(length);

to:

length = get_length(length);

There's no need to pass length when you do this.

The other way to do it is to pass an address:

#include 

void get_length(double * a);

int main(int argc, char* argv[]) {
    double length = 0;
    get_length(&length);
    printf("%f", length);
    return 0;
}

void get_length(double * a) {
    printf("What is the rectangle's length?\n");
    scanf("%lf", a);
}

Note that %f, not %lf, is the correct format specifier for a double in printf(). Using %lf is correct for scanf(), however.