C Program to Find Sum of N Numbers

Howdy readers, today you will learn how to write a program to find the sum of N numbers using the C Programming language.

The below program prompts the user to enter total number of integers to add, then this program find the sum of all integers using the following methods:

1. Using For Loop
2. Using While Loop
3. Using Do While Loop
4. Using User-defined Function
5. Using Recursion
6. Integers Entered by the User

So, without any delay, let’s begin this tutorial.

C Program to Find Sum of N Numbers

C Program

// C Program to Find Sum of N Numbers
#include <stdio.h>
int main(){
    int num, sum = 0;
    
    // Taking input
    printf("Enter the no. of integers to add: ");
    scanf("%d", &num);
    
    // Calculating the sum
    for (int i = 1; i <= num; i++){
        sum = sum + i;
    }
    
    // Displaying result
    printf("Sum of %d natural numbers: %d", num, sum);
    
    return 0;
}

Output

Enter the no. of integers to add: 25
Sum of 25 natural numbers: 325

Explanation

    int num, sum = 0;

In the above program, we have declared two int data type variables named num and sum. The sum variable has assigned a value of 0.

    // Taking input
    printf("Enter the no. of integers to add: ");
    scanf("%d", &num);

We take input from the user. This number gets stored in the ‘num’ named variable.

    // Calculating the sum
    for (int i = 1; i <= num; i++){
        sum = sum + i;
    }

For every iteration, we add the value of i with sum. After each iteration, the value of i gets incremented by 1. This loop keeps executing until i is equal to or less than the entered integer num.

This gives us the sum of all numbers lying from 1 to the entered integer.

    // Displaying result
    printf("Sum of %d natural numbers: %d", num, sum);

The sum of N numbers is displayed on the screen using printf() function.

C Program to Find Sum of N Numbers Using While Loop

C Program

// C Program to Find Sum of N Numbers Using While Loop
#include <stdio.h>
int main(){
    int num, sum = 0;
    
    // Taking input
    printf("Enter the no. of integers to add: ");
    scanf("%d", &num);
    
    int i = 1;
    while (i <= num){
        sum = sum + i;
        i++;
    }
    
    // Displaying result
    printf("Sum of %d numbers: %d", num, sum);
    
    return 0;
}

Output

Enter the no. of integers to add: 12
Sum of 12 numbers: 78

Explanation

    while (i <= num){
        sum = sum + i;
        i++;
    }

Within the while loop, for each iteration we add the sum with i. After each iteration, the value is incremented by 1 until i is less than or equal to num.

C Program to Find Sum of N Numbers Using Do While Loop

C Program

// C Program to Find Sum of N Numbers Using Do While Loop
#include <stdio.h>
int main(){
    int num, sum = 0;
    
    // Taking input
    printf("Enter the no. of terms: ");
    scanf("%d", &num);
    
    int i = 1;
    
    // Computing the sum
    do {
        sum = sum + i;
        i++;
    } while (i <= num);
    
    // Displaying result
    printf("Sum of %d numbers: %d", num, sum);
    
    return 0;
}

Output

Enter the no. of terms: 5
Sum of 5 numbers: 15

Explanation

    // Computing the sum
    do {
        sum = sum + i;
        i++;
    } while (i <= num);

The logic is the same as that of the above two programs, this loop keeps executing until i <= num.

C Program to Find Sum of N Numbers Using Functions

C Program

// C Program to Find Sum of N Number Using Function
#include <stdio.h>
int findSum(int);

int main(){
    int num, result;
    
    // Taking input
    printf("Enter total no. of integers: ");
    scanf("%d", &num);
    
    // Calling out function
    result = findSum(num);
    
    // Displaying result
    printf("Sum of %d numbers: %d", num, result);
    
    return 0;
}

int findSum(int n){
    int i = 1, sum = 0;
    
    while(i <= n){
        sum = sum + i;
        i++;
    }
    return sum;
}

Output

Enter total no. of integers: 7
Sum of 7 numbers: 28

Explanation

int findSum(int n){
    int i = 1, sum = 0;
    
    while(i <= n){
        sum = sum + i;
        i++;
    }
    return sum;
}

In the above program, we have defined a custom function named findSum which computes and returns the sum using a simple do while loop.

Then, we call this custom function in the main function and print the sum on the screen.

C Program to Find Sum of N Number Using Recursion

C Program

// C Program to Find Sum of N Numbers Using Recursion
#include <stdio.h>
int calculateSum(int n);

int main(){
    int num, answer;
    
    // Taking input
    printf("Enter total no. of numbers: ");
    scanf("%d", &num);
    
    // Calling out recursive function
    answer = calculateSum(num);
    
    // Displaying result
    printf("Sum of %d numbers: %d", num, answer);
    
    return 0;
}

int calculateSum(int n){
    if (n == 0)
        return n;
    else
        return (n + calculateSum(n - 1));
}

Output

Enter total no. of numbers: 10
Sum of 10 numbers: 55

Explanation

int calculateSum(int n){
    if (n == 0)
        return n;
    else
        return (n + calculateSum(n - 1));
}

In this program, we have defined a recursive function named calculateSum which finds the sum by calling out the recursive function.

C Program to Find Sum of N Number When Integers are Entered by the User

C Program

// C Program to Find Sum of N Numbers When Integers are Entered By the User
#include <stdio.h>
int main(){
    int num, n, sum = 0;
    
    // Taking input
    printf("Enter total no. of terms: ");
    scanf("%d", &num);
    printf("Enter the elements: \n");
    for (int i = 0; i < num; i++){
        scanf("%d", &n);
        sum = sum + n;
    }
    
    // Displaying result
    printf("Sum = %d", sum);
    
    return 0;
}

Output

Enter total no. of terms: 3
Enter the elements: 
6
9
45
Sum = 60

Conclusion

I hope after reading this tutorial, you understand how to write a program to find the sum of n numbers using C Programming language.

If you have any queries regarding the tutorial, then let us know in the comment section. We will be pleased to solve all of your queries.