# C Exercises: Check whether a number can be express as sum of two prime numbers

## C For Loop: Exercise-56 with Solution

Write a program in C to check whether a number can be expressed as the sum of two prime.

Visual Presentation: Sample Solution:

C Code:

``````#include <stdio.h>   // Include the standard input/output header file.
#include <stdlib.h>
#include <math.h>   // Include the math header file.
int main()
{
// Variable declarations
int num, i, j, temp1, temp2, ctr=0;
// Prompting user for input
printf("input the number:\n");
// Getting user input
scanf("%d", &num);
// Loop to find pairs of numbers that add up to 'num'
for(i = 2; i<= num/2; i++){
temp1 = i;
temp2 = num - i;
// Checking if 'i' is a prime number
for(j = 2; j <= i/2; j++){
if(i % j == 0){
ctr++;
break;
}
}
// If 'i' is a prime number, check if 'num - i' is also prime
if(ctr == 0){
for(j = 2; j <= (num - i)/2; j++){
if((num - i) % j == 0){
ctr++;
break;
}
}
// If both 'i' and 'num - i' are prime, print the pair
if(ctr == 0)
printf("%d can be written as %d + %d.\n ", num, i, num - i);
}
// Resetting the counter
ctr = 0;
}
return 0;
}
```
```

Sample Output:

```input the number: 16
16 can be written as 3 + 13.
16 can be written as 5 + 11.
```

Flowchart: C Programming Code Editor:

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