次の例は、primain.cファイルの内容を示しています。

#include <stdio.h>
#include "primelib.h"

/*
 * Nominal C program churning to provide a code base we might want to
 * instrument with D
*/

// Search for a divisor -- thereby proving composite value of the input.
int main()  {
  int targVal, divisor, factorA=0, factorB=0;

  printf( "Enter a positive target integer to test for prime status: " );
  scanf( "%d", &targVal );

  // Check that the user input is valid
  if( targVal < 2 ) {
    printf( "Invalid input value -- exiting now\n" );
    return -2;
  }

  // Search for a divisor using method and function A
  int lastCheck;
  lastCheck = findMaxCheck( targVal );
  printf( "%d highest value to check as divisor\n", lastCheck );
  factorA = seekFactorA( targVal, lastCheck );

  // Search for a divisor using method and function B
  factorB = seekFactorB( targVal );

  // Warn if the methods give different results
  if (factorA != factorB)
    printf( "%d does not equal %d! How can this be?\n", factorA, factorB );

  // Print results
  if( !factorA )
    printf( "%d is a prime number\n", targVal );
  else
    printf( "%d is not prime because there is a factor %d\n",
	    targVal, factorA );
  return 0;
}