C Programming Code Examples C > For Loops and While Loops Code Examples C program to find sum of prime numbers between 1 to n C program to find sum of prime numbers between 1 to n Write a C program to find sum of all prime numbers between 1 to n using for loop. C program to generate sum of all primes between a given range. Logic to find sum of prime numbers in a given range. What is Prime number? Prime numbers are positive integers greater than 1 that has only two divisors 1 and the number itself. For example: 2, 3, 5, 7, 11 are the first 5 prime numbers. Logic to find sum of prime numbers between 1 to n Input upper limit to find sum of prime from user. Store it in some variable say end. Initialize another variable sum = 0 to store sum of prime numbers. Run a loop from 2 to end, incrementing 1 in each iteration. The loop structure should look like for(x=2; x<=end; x++). Inside the loop check if loop counter variable is prime or not. If x is prime then add x to sum i.e. sum = sum + x. Finally after loop print the resultant value of sum. #include <stdio.h> int main() { int x, j, end, isPrime, sum=0; /* Input upper limit from user */ printf("Find sum of all prime between 1 to : "); scanf("%d", &end); /* Find all prime numbers between 1 to end */ for(x=2; x<=end; x++) { /* Check if the current number x is Prime or not */ isPrime = 1; for(j=2; j<=x/2 ;j++) { if(x%j==0) { /* 'x' is not prime */ isPrime = 0; break; } } /* If 'x' is Prime then add to sum */ if(isPrime==1) { sum += x; } } printf("Sum of all prime numbers between 1 to %d = %d", end, sum); return 0; }