/* ECP: FILEname=fig3_24.c */
/* 1*/   /* Find Next Prime After Some Starting Number */

/* 2*/   #include <stdio.h>
/* 3*/   #define TRUE 1

/* 4*/   main( void )
/* 5*/   {
/* 6*/       unsigned long int Divisor, PossiblePrime;
/* 7*/       int FoundPrime;

/* 8*/       printf( "Enter the starting number: " );
/* 9*/       scanf( "%lu", &PossiblePrime );

/*10*/       if( PossiblePrime <= 2 )
/*11*/           PossiblePrime = 2;
/*12*/       else
/*13*/       if( PossiblePrime != 3 )
/*14*/       {
/*15*/           if( PossiblePrime % 2 == 0 )
/*16*/               PossiblePrime++;	/* Need An Odd Number */

/*17*/           for( ; ; PossiblePrime += 2 )
/*18*/           {
/*19*/               FoundPrime = !TRUE;
/*20*/               for( Divisor = 3; PossiblePrime % Divisor; Divisor += 2 )
/*21*/                   if( Divisor * Divisor > PossiblePrime )
/*22*/                   {
/*23*/                       FoundPrime = TRUE;
/*24*/                       break;
/*25*/                   }
/*26*/       
/*27*/               if( FoundPrime )
/*28*/                   break;
/*29*/           }
/*30*/       }

/*31*/       printf( "Next largest prime is %lu\n", PossiblePrime );
/*32*/   }