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-   -   Prime numbers..problem with code (http://www.go4expert.com/forums/prime-numbersproblem-code-t2101/)

zeeshan 2Dec2006 03:43

Prime numbers..problem with code
 
hi friends, im a newbie at C,

im trying to code for a program which cud return all prime numbers in a specific range.

its returning the results with an error, which is , it also includes the products of two prime numbers in results,
for example 15=3*5 and 21=3*7

my code is
---------------------------------------------------------
Code:

#include<conio.h>
#include<stdio.h>
void main()
{
clrscr();
for (int i=1;i<=300;i++)
 {
  for(int j=2;j<=i;j++)
  if(i%j==0 )

  break;
  else
      {
        printf("\t%d ",i);
        break;
        }
  }
getche();
}

--------------------------------------------------
Result:

3 5 7 9 11 13 15 17 19 21 23 .................

kindly guide me where the problem resides.
which is letting 15,21 etc in output.

pradeep 2Dec2006 10:48

Re: Prime numbers..problem with code
 
Here is the code for finding a prime number in a specified range.

Code: C

#include <stdio.h>
#include <math.h>
// The range of numbers where you want to look for prime numbers
#define RANGE_MIN 2
#define RANGE_MAX 100

void main(void)
{
    int i,j,sq,is_prime;

    for(i=RANGE_MIN;i<=RANGE_MAX;i++)
    {

        is_prime = 1;
        sq = sqrt(i); // calculate the square root
        for(j=2;j<=sq;j++)
        {
            if(i%j==0)
                is_prime = 0;
        }

        if(is_prime)
            printf("%d, ",i);
    }
}


Also checkout this thread http://www.go4expert.com/showthread.php?t=2049

friendsforniraj 2Dec2006 18:20

Re: Prime numbers..problem with code
 
thats great now


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