Question

I ran the following:

#include <stdio.h>
typedef unsigned short boolean;

#define false 0
#define true (!false)
int main()
{
    int STATUS = 0;
    int i = 0;
    boolean ret = true;
    for(i = 0; i < 99999; i++)
    {
        ret = ret && printf("Hello, World.");
    }
    if(!ret)
    {
        STATUS = -1;
    }

    return STATUS;
}

It completes in just under a second. Typically 0.9 – 0.92.

Then I changed int i = 0; to int *i = 0; and now I am getting execution times under 0.2 seconds. Why the speed change?

Answer 1

Your runtime is dominated by the time required to print to the console. i++ on an int* will increment the pointer by the size of a pointer. That will be either 4 or 8 depending on your computer and compiler settings. Based on the numbers you report, presumably it would be 4. So printf is executed only a quarter as many times.