Need Some Coaching, Display 100 Prime Numbers

I've been working at this for awile and I need some help. I can print the first 100 non-prime numbers but not the first 100. What am I missing? This nested loop business is killing me. Here is what I have:

Code:

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#include<stdio.h>

int main (void)
{
    int num, test;
        int prime = 0;
        int not_prime = 0;

        for (num = 2; num < 100; num++)
        {
               
                for (test = 2; test < (num - 1); test++)
                       
                {
                                        if (num % test == 0)
                                {
                                        printf ("%d\n", num);
                                        break;
                                }
                }
                //printf ("%d\n", num);       
                       
                }
        }

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Quote:

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I can print the first 100 non-prime numbers but not the first 100

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Huh?

Also, clean up your whitespace. Makes it easier to read...for everyone!

Not the first 100 prime.

Do you want to print out non-prime numbers? I don't know what your requirements are. You never stated them clearly.

Regardless, you need to work out on paper how you'd do this as if you were a computer. Flowchart it , then write the code.

Throwing loops together haphazardly is a recipe for disaster.

I want to print the first 100 prime numbers. I am able to do the all of the non primes from 0 to 100 but cannot figure out how to get the primes. This is what I think I need to do.

Make a loop that goes from 2 to 100.
Make another loop that will test each value by using modulus 2 to the number -1
If any 0's are found, the number is not prime
If no zeroes are found the number is prime

I can't figure out how to catch the primes. Actually I have caught them a couple times but they print for every trip through the loop. I can;t figure out how to just catch them one at a time.

See bold

Quote:

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Originally Posted by dolfaniss

Make a loop that goes from 2 to 100.
Make another loop that will test each value by using modulus 2 to the number -1
If any 0's are found, the number is not prime <---set a flag variable (say, prime_found ) and break from the loop either directly, or by the test at the top of the loop
If no zeroes are found the number is prime

I can't figure out how to catch the primes. Actually I have caught them a couple times but they print for every trip through the loop. I can;t figure out how to just catch them one at a time.

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Something like this (not tested)

Code:

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    prime_found = FALSE;
    for (test = 2; test < (num - 1); test++) {
        if (num % test == 0) {
            prime_found = TRUE;
            break;
        }
    }
    if (prime_found) {
        printf ("%d\n", num);
    }

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Thanks Mike, I will play around and see what I can come up with.