Check if prime number using recursive and no loop in turbo c

Question

Good Day,

I'm trying to make a code that would determine the prime numbers between two numbers. This should be done recursively and without any loop. So far I have this code:

#include<stdio.h>
#include<conio.h>
void prime(int x, int y){
    int waa;
    if(x <= y){
        waa = isPrime(x);
        if(waa==1 || waa == 0){
             printf("");
         }else{
             printf("%5d",waa);
         }
        prime(x+1,y);
    }
}

int isPrime(int n, int i){
    i = 2;
    if(i<n){
        if(n%i==0 && n!=2 && n!=i){
         return(0);
        }else{
            return(n);
        }
         i++;
         isPrime(n,i);      
    }
}

void main(){
    int num[2];
    clrscr();

    printf("Input 2 numbers: \n");
    scanf("%d %d", &num[0], &num[1]);
    prime(num[0], num[1]);
    getch();
}

the output between 1 and 10 is: 2,2,3,5,7,9. expected output: prime numbers 2,3,5,7

Would anyone be able to help me with this.

much appreciated

Thank you

Answer 1

It will be simpler if function isPrime just checks whether the given integer is prime or not and outputs a Boolean value.

#include<stdio.h>
#include <math.h>

void prime(int x, int y){
    int waa;
    if ( x == 1 ) x++;
    if(x <= y){
        waa = isPrime(x,2); // second input parameter added
        if(waa != 0){
            printf("%5d",x);
         }
        prime(x+1,y);
    }
}

int isPrime(int n, int i){
    if(n%i==0 && n!=2 && n!=i){
      return(0);
    } else {
       if (i < sqrt(n)) {
            return( isPrime(n,i+1) );
        } else
         return 1;
    }
}

int main(){
    int num[2];

    printf("Input 2 numbers: \n");
    scanf("%d %d", &num[0], &num[1]);
    prime(num[0], num[1]);
    return 0;
}

Input:

1
10

Output:

2 3 5 7

http://ideone.com/gyW7ED