Thread: Newbie with trouble

I am stuck on this problem that I am trying to solve in this book tha I am reading on C programming. I am new to C and I could use some help to understand how to solve this ....thanks in advance.

The problem has these requirements.
1. Prompt user for a limit.
2. start from 1.....limit.
3. for each number test to see if it retruns a remainder
from dividing by 2...3...4...5...until half of the number.
4. if after any division ...it returns a 0 remainder....skip it
5. otherwise print it as a prime number.

This probably seems very simple to most of you but I have a headache from thinking about it for so long.

I have so far :

#include <stdio.h>

int i,
j,
num;

int main()
{

printf("Enter your Limit:");
scanf("%d",&num);
for(i=1; i<num;i++)
{
for(j = 1;j<(i/2);j++)
{
if((i % j) != 0)
continue;
}
printf("\n%d is prime",i);
}
return(0);
}

Your code is basically right except for two points...

3. for each number test to see if it retruns a remainder
from dividing by 2...3...4...5...until half of the number

This means you need to start the j loop with j = 2, not j = 1, since i%1 == 0 for all i.

Also, your use of continue inside that for loop is going to cause problems... that is, it's going to make the loop do nothing. Here's what I suggest...

Code:

for(j = 2; j < (i / 2); j++)
{
 if ((i % j) == 0) break; // Terminate loop if factor of j is found.
}
if (j == i / 2) // If loop was terminated due to 
                    //  j going beyong loop limits...
printf("\n%d is prime",i);

Continue does not terminate a loop. All it does is force the next iteration of a loop.