C program calculates the sum of natural numbers

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In this example, you will learn to calculate the sum of natural numbers entered by the user.

To understand this example, you should know the followingC programming languageTopic:

• C for loop

• C while and do ... while loops

Positive numbers1,2,3 ...Called natural numbers. Not exceeding10The sum of natural numbers is:

sum =　1　+　2　+　3　+　...　+　10

Natural number sum using a for loop

#include <stdio.h>
int main() {
　　　　int n, i, sum = 0;
　　　　printf("Enter a positive integer: ");
　　　　scanf("%d", &n);
　　　　for (i =　1; i <= n;　++i) {
　　　　　　　　sum　+= i;
　　　　}
　　　　printf("Sum = %d", sum);
　　　　return 0;
}

The above program gets input from the user and stores it in the variable n. Then, it uses a for loop to calculate the sum of n.

Natural number sum using a while loop naturally

#include <stdio.h>
int main() {
　　　　int n, i, sum = 0;
　　　　printf("Enter a positive integer: ");
　　　　scanf("%d", &n);
　　　　i =　1;
　　　　while (i <= n) {
　　　　　　　　sum　+= i;
　　　　　　　　++i;
　　　　}
　　　　printf("Sum = %d", sum);
　　　　return 0;
}

Output the result

Enter a positive integer:　100
Sum =　5050

In both programs, the loop is iterated n times. In each iteration, the value of i is added to sum and i is incremented1.

Although both programs are technically correct, it is better to use a for loop in this case. Because the number of iterations is known.

If the user enters a negative integer, the above program cannot work properly. Here, a slight modification has been made to the above program. In this program, we keep getting input from the user until a positive integer is entered.

Read input until a positive integer is entered

#include <stdio.h>
int main() {
　　　　int n, i, sum = 0;
　　　　do {
　　　　　　　　printf("Enter a positive integer: ");
　　　　　　　　scanf("%d", &n);
　　　　} while (n <= 0);
　　　　for (i =　1; i <= n;　++i) {
　　　　　　　　sum　+= i;
　　　　}
　　　　printf("Sum = %d", sum);
　　　　return 0;
}

Visit this page to learnHow to use recursion to find the sum of natural numbers.

Comprehensive Collection of C Programming Examples