# 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.

Example

Input

`Input upper limit: 10`

Output

`Sum of prime numbers between 1-10: 17`

## Required knowledge

### 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

Step by step descriptive logic to find sum of prime numbers between 1 to n.

1. Input upper limit to find sum of prime from user. Store it in some variable say end.
2. Initialize another variable `sum = 0` to store sum of prime numbers.
3. Run a loop from 2 to end, incrementing 1 in each iteration. The loop structure should look like `for(i=2; i<=end; i++)`.
4. Inside the loop check if loop counter variable is prime or not. If i is prime then add i to sum i.e. `sum = sum + i`.
5. Finally after loop print the resultant value of sum.

## Program to find sum of prime numbers between 1 to n

``````/**
* C program to find sum of prime numbers between 1 to n
*/

#include <stdio.h>

int main()
{
int i, 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(i=2; i<=end; i++)
{

/* Check if the current number i is Prime or not */
isPrime = 1;
for(j=2; j<=i/2 ;j++)
{
if(i%j==0)
{
/* 'i' is not prime */
isPrime = 0;
break;
}
}

/*
* If 'i' is Prime then add to sum
*/
if(isPrime==1)
{
sum += i;
}
}

printf("Sum of all prime numbers between 1 to %d = %d", end, sum);

return 0;
}``````

## Program to find sum of prime numbers in given range

``````/**
* C program to find sum of prime numbers in given range
*/

#include <stdio.h>

int main()
{
int i, j, start, end;
int isPrime, sum=0;

/* Input lower and upper limit from user */
printf("Enter lower limit: ");
scanf("%d", &start);
printf("Enter upper limit: ");
scanf("%d", &end);

/* Find all prime numbers in given range */
for(i=start; i<=end; i++)
{

/* Check if the current number i is Prime or not */
isPrime = 1;
for(j=2; j<=i/2 ;j++)
{
if(i%j==0)
{
/* 'i' is not prime */
isPrime = 0;
break;
}
}

/*
* If i is Prime then add to sum
*/
if(isPrime==1)
{
sum += i;
}
}

printf("Sum of all prime numbers between %d to %d = %d", start, end, sum);

return 0;
}``````

Output

```Enter lower limit: 10
Enter upper limit: 20
Sum of all prime numbers between 10 to 20 = 60```

Happy coding ðŸ˜‰