function 1

#include<stdio.h>

int checkPrimeNumber(int n);  //return_type function_name (parameters)

@@@

int main()

#include<stdio.h>

int checkPrimeNumber(int n);  //return_type function_name (parameters)

@@@

int main()

{

    int n1, n2, i, flag;

    printf("Enter two positive integers: ");

    scanf("%d %d", &n1, &n2);

    printf("Prime numbers between %d and %d are: ", n1, n2

    for(i=n1+1; i<n2; ++i)

    {

        // i is a prime number, flag will be equal to 1

        flag = checkPrimeNumber(i);

        if(flag == 1)

            printf("%d ",i);

    }

    return 0;

}

// user-defined function to check prime number

int checkPrimeNumber(nt n) ////return_type function_name (parameters)

{

    int j, flag = 1;

    for(j=2; j <= n/2; ++j)

    {

        if (n%j == 0)

        {

            flag =0;

            break;

        }

    }

    return flag;

}

Output

Enter two positive integers: 12
30
Prime numbers between 12 and 30 are: 13 17 19 23 29