text: two prime numbers −
  
   Live Demo
  
  #include <stdio.h>
  int Sum(int n);
  int main(){
     int num, i;
     printf("Enter number: ");
     scanf("%d", &num);
     int flag = 0;
     for(i = 2; i <= num/2; ++i){
        if (sum(i) == 1){
           if (sum(num-i) == 1){
              printf("\nThe given %d can be expressed as the sum of %d and %d\n\n", num, i, num - i);
              flag = 1;
           }
        }
     }
     if (flag == 0)
     printf("The given %d cannot be expressed as the sum of two prime numbers\n", num);
     return 0;
  }
  
  int sum(int n){
     int i, isPrime = 1;
     for(i = 2; i <= n/2; ++i){
        if(n % i == 0){
           isPrime = 0;
           break;
        }
     }
     return isPrime;
  }
  