```
void main(void)
{
unsigned int a=100, b=500; // a and b are the two numbers...
unsigned int i,j,s=0,is_prime;
for(i=a;i<=b;i++)
{
is_prime = 1; // Assuming that current value of i is prime
// Checking for prime
for(j=2;j<=(i/2);j++)
{
if(i%j==0) // Not prime, set is_prime to 0 and break
{
is_prime = 0;
break;
}
}
if(is_prime) // If the number is prime, sum it up
{
s += i;
}
}
printf("\n\nThe sum of the prime numbers = %d",s);
}
```