C program to find sum of prime numbers between 1 to n

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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.

Required knowledge

Basic C programming, If else, For loop, Nested loops

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

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