Question

In the following code, in the innermost loop, when d < p is true and p % d == 0 is false,
is variable d being incremented or is incrementing being skipped?

// Program to generate a table of prime numbers

#include <stdio.h>

int main (void)
{
    int p, d;
    _Bool isPrime;

    for ( p = 2; p <= 50; ++p ) {
        isPrime = 1;

        for ( d = 2; d < p; ++d )
            if ( p % d == 0 )
                isPrime = 0;

            if ( isPrime != 0 )
                printf ("%i  ", p);
    }
    printf ("\n");
    return 0;
}

Answer 1

When d < p is true then d is being incremented. That’s the only condition that matters, not whether or not the modulus has a value.

Also not that it matters but why not declare d and p inside the loop

int p = 2; p <= 50; ++p

int d = 2; d < p; ++d 

Not that it matters much but it’s nice to limit the scope of the variables if you aren’t going to use them after the loop