C program to display the prime numbers in between two intervals

Enter two numbers at console during runtime. Then, declare the flag variable which is used to check whether the number is prime or not with the help of for loop condition.

Whenever, the flag is zero, it prints the prime number and if flag is one, it exists from the loop.

Program

Following is the C program to display the prime numbers in between two intervals −

 Live Demo

#include <stdio.h>
int main(){
   int number1,number2,i,j,flag;
   printf("enter the two intervals:");
   scanf("%d %d",&number1,&number2);
   printf("prime no’s present in between %d and %d:",number1,number2);
   for(i=number1+1;i<number2;i++){// interval between two numbers
      flag=0;
      for(j=2;j<=i/2;++j){ //checking number is prime or not
         if(i%j==0){
            flag=1;
            break;
         }
      }
      if(flag==0)
         printf("%d
",i);
   }
   return 0;
}

Output

You will see the following output −

enter the two intervals:10 50
the number of prime numbers present in between 10 and 50:11
13
17
19
23
29
31
37
41
43
47

Consider another example, wherein, we are trying to remove the prime numbers in between two numbers.

Example

Following is the C program to display the numbers in between two intervals excluding prime numbers −

 Live Demo

#include <stdio.h>
int main(){
   int number1,number2,i,j,flag;
   printf("enter the two intervals:");
   scanf("%d %d",&number1,&number2);
   printf("the numbers that are present after removing prime numbers in between %d and %d:
",number1,number2);
   for(i=number1+1;i<number2;i++){// interval between two numbers
      flag=1;
      for(j=2;j<=i/2;++j){ //checking number is prime or not
         if(i%j==0){
            flag=0;
            break;
         }
      }
      if(flag==0)
         printf("%d
",i);
   }
   return 0;
}

Output

You will see the following output −

enter the two intervals:10 20
the numbers that are present after removing prime numbers in between 10 and 20:
12
14
15
16
18