Finding Prime Numbers In C++ Language

One of the frequent headache in the world of mathematics is to determine whether a number is prime or not. This time will be given examples of programs to find or check whether a number is included in the primes.
As is well known, prime number is a number that is only divisible by 1 and the number itself. Numbers 1 because it is a divider factor can not be called a prime number. Then as a starting point the calculation, the smallest prime number that must be known. In this case will be taken number 2 and 3 as the smallest prime number. Number 2 is a prime number which is unique because it is the only even prime. The other primes must be odd (odd).

Well, simply, a program to find prime numbers are given on the listing..

Listing 1. Finding primes:

#include <stdio.h>

main()

{

int bilangan;

int prima;

int cekprima();

clrscr();

printf("======================\n");

printf("FIND PRIMA NUMBERS\n");

printf("======================\n\n");

printf("Enter an integer : ");

scanf("%d",&number);

prima = cekprima(number);

if (prima == 1)

{

printf("number %d is prime",number);

} else {

printf("number %d not a prime number",number);

}

}

int cekprima(bil)

int bil;

{

int toward=3;

int boundary;

if (bil == 1)

{

return(0);

} else if (bil==2||bil==3) {

return(1);

} else if (bil % 2 == 0) {

return(0);

} else {

while (boundary > toward)

{

if (bil % toward == 0)

{

printf("Because the divisible %d\n",toward);

return(0);

break;

}

boundary = bil / toward;

toward += 2;

}

return(1);

}

}

Listing 2. Finding primes in the range 1-1000

#include <stdio.h>

main()

{

int i;

int prima;

int cekprima();

clrscr();

printf("======================\n");

printf("FIND PRIMA NUMBERS\n");

printf("in the range 1-1000\n");

printf("======================\n\n");

printf("Primes found : \n");

for (i=1;i<=1000;i++)

{

prima = cekprima(i);

if (prima == 1)

{

printf(" %d",i);

}

}

}

int cekprima(bil)

int bil;

{

int bagi=3;

int batas;

if (bil == 1)

{

return(0);

} else if (bil==2||bil==3) {

return(1);

} else if (bil % 2 == 0) {

return(0);

} else {

while (batas > bagi)

{

if (bil % bagi == 0)

{

return(0);

break;

}

batas = bil / bagi;

bagi += 2;

}

return(1);

}

}