Where is my Code Wrong

so i need my program to display only palindromic prime numbers but its just displaying prime numbers and not displaying only palindroimc primes

Code:

 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
 #include <string.h>
 #include<math.h>
  FILE *outputFile;
  char buffer[81];
  int bytesWritten;

 main()
 {
  int isPrime(int);

  int i,j;

  long int n, num, rev = 0, dig;

   /*************************************/
 /*     Open file to write output     */
 /*************************************/
 outputFile = fopen("DD:OUTPUT", "w");
 if (outputFile == NULL)
 {
  printf("open error:   %d/%s\n", errno, strerror(errno));
  exit(99);
 }

 /*************************************/
 /*     Run program                   */
 /*************************************/

  for (i=1; i<15000; i++)

    {
    if (isPrime(i)==1)
    {
     n = num;
     while(num>0)
     {
          dig = num % 10;
          rev = rev * 10 + dig;
          num = num / 10;
     }
     if (n == rev)


     bytesWritten = sprintf(buffer,"%d is prime!!\n",i);
     fwrite(buffer, 1, bytesWritten, outputFile);
    }
  }



 /*************************************/
 /*     Close output file             */
 /*************************************/
 fclose(outputFile);

  return 0;
}

int isPrime (int myInt)
{


  int loop;

  for (loop = 2; loop < myInt/2+1; loop++)
  {
    if (myInt%loop==0)
      return 0;
  }
    return 1;
 }

Your offending code is

Code:

     if (n == rev)


     bytesWritten = sprintf(buffer,"%d is prime!!\n",i);
     fwrite(buffer, 1, bytesWritten, outputFile);

This will always produce output, regardless of whether the value is palindromic. An extra curly brace or two would fix your problem.

It is rather pointless to open DD:OUTPUT and use fwrite() to produce output. Better to use standard text output to stdout. And it is advisable to declare main as returning int, rather than relying on implicit return type.

an extra curly brace where?

Originally Posted by grumpy

Your offending code is

Code:

     if (n == rev)


     bytesWritten = sprintf(buffer,"%d is prime!!\n",i);
     fwrite(buffer, 1, bytesWritten, outputFile);

This will always produce output, regardless of whether the value is palindromic. An extra curly brace or two would fix your problem.

It is rather pointless to open DD:OUTPUT and use fwrite() to produce output. Better to use standard text output to stdout. And it is advisable to declare main as returning int, rather than relying on implicit return type.

I have given you all the hints necessary. You can work out, for yourself, where curly braces are needed.

After all, this is your homework.