Functions Programs — C language

Write a program in C to check whether a number is a prime number or not using the function.

#include<stdio.h>
int PrimeOrNot(int);
int main()
{
    int n1,prime;
    printf("\n\n Function : check whether a number is prime number or not :\n");
    printf(" Input a positive number : ");
    scanf("%d",&n1);
    prime = PrimeOrNot(n1);
    if(prime==1)
        printf(" The number %d is a prime number.\n",n1);
    else
      printf(" The number %d is not a prime number.\n",n1);
    return 0;
}
int PrimeOrNot(int n1)
{
    int i=2;
    while(i<=n1/2)
    {
         if(n1%i==0)
             return 0;
         else
             i++;
    }
    return 1;
}

Write a program in C to check Armstrong and Perfect numbers using the function. (three-digit Program)

#include <stdio.h>
 
int checkArmstrong(int n1);
int checkPerfect(int n1);
 
int main()
{
    int n1;
    printf("\n\n Function : check Armstrong and perfect numbers :\n");

     
    printf(" Enter any number: ");
    scanf("%d", &n1);

    if(checkArmstrong(n1))
    {
        printf(" The %d is an Armstrong number.\n", n1);
    }
    else
    {
        printf(" The %d is not an Armstrong number.\n", n1);
    }
    if(checkPerfect(n1))
    {
        printf(" The %d is a Perfect number.\n\n", n1);
    }
    else
    {
        printf(" The %d is not a Perfect number.\n\n", n1);
    }
    return 0;
}
int checkArmstrong(int n1) 
{
    int ld, sum, num;
    sum = 0;
    num = n1;
    while(num!=0)  
    {  
        ld = num % 10;  
        sum += ld * ld * ld; 
        num = num/10;  
    }
    return (n1 == sum);
}
int checkPerfect(int n1) 
{
    int i, sum, num;
    sum = 0;
    num = n1;
    for(i=1; i<num; i++)  
    {  
        if(num%i == 0)  
        {  
            sum += i;  
        }  
    }
    return (n1 == sum);
}

Write a program in C to print all perfect numbers in a given range using the function.

#include <stdio.h>

int checkPerfect(int );
void PerfectNumbers(int , int );

int main()
{
    int st, en;
    printf("\n\n Function : perfect numbers in a given range :\n");   
    printf(" Input lowest search limit of perfect numbers : ");
    scanf("%d", &st);
    printf(" Input highest search limit of  perfect numbers : ");
    scanf("%d", &en);
     
    printf("\n The perfect numbers between %d to %d are : \n", st, en);
    PerfectNumbers(st, en);
    return 0;
}
int checkPerfect(int n1)
{
    int i, sum;
     
    sum = 0;
    for(i=1; i<n1; i++)
    {
        if(n1 % i == 0)
        {
            sum += i;
        }
    }
    if(sum == n1)
        return 1;
    else
        return 0;
}

void PerfectNumbers(int st, int en)
{
    while(st <= en)
    {
        if(checkPerfect(stLimit))
        {
            printf(" %d  ", st);
        }
        st++;
    }   
}