C program to find whether the given number is prime or composite

 Program code

#include <stdio.h>

#include <conio.h>

void main()

{

int question=0, i=2;

clrscr();

printf(“Please input a positive integer to find out whether it is a prime number or composite number.\n”);

scanf(“%d”,&question);

if (question==1)

{

printf(“%d is neither prime nor composite.\n”, question);

goto stop;

}

if (question==2)

{

printf(“%d is a prime number.\n%d is the only even prime number.\n”,question,question);

goto stop;

}

do

{

if (question%i==0)

{

printf(“%d is a composite number.\n”,question);

goto stop;

}

i++;

}

while(i<question);

printf(“%d is a prime number.\n”,question);

stop:

getch();

}

Example of output

Please input a positive integer to find out whether it is a prime number or composite number.

3

3 is a prime number

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