C Program: Calculate Sum of positive integers using Do-While Loop

Last update on July 30 2025 12:56:19 (UTC/GMT +8 hours)

2. Sum of Positive Integers Until 0

Write a C program that prompts the user to input a series of integers until the user stops by entering 0 using a do-while loop. Calculate and print the sum of all positive integers entered.

Sample Solution:

C Code:

#include <stdio.h>

int main() {
    int num, sum = 0;  // Declare variables to store the entered number and the sum

    // Prompt the user to input integers until they enter 0
    do {
        printf("Input an integer (enter 0 to stop): ");
        scanf("%d", &num);  // Read the entered number

        if (num > 0) {
            sum += num;  // Add the positive number to the sum
        } else if (num < 0) {
            printf("Negative integers are not considered. Ignored.\n");
        }

    } while (num != 0);  // Continue the loop until the user enters 0

    // Print the sum of positive integers
    printf("Sum of positive integers: %d\n", sum);

    return 0;  // Indicate successful program execution
}

Sample Output:

Input an integer (enter 0 to stop): 4
Input an integer (enter 0 to stop): 3
Input an integer (enter 0 to stop): 2
Input an integer (enter 0 to stop): -7
Negative integers are not considered. Ignored.
Input an integer (enter 0 to stop): 5
Input an integer (enter 0 to stop): 0
Sum of positive integers: 14

Explanation:

Here is the break down of the above code step by step:

#include <stdio.h>: This line includes the standard input-output library, which is necessary for using functions like "printf()" and "scanf()".
int main() {: This line marks the beginning of the "main()" function, which is the entry point of every C program.
int num, sum = 0;: This line declares two integer variables, 'num' to store the entered number, and 'sum' to store the sum of positive integers. 'sum' is initialized to 0.
// Prompt the user to input integers until they enter 0: Comment indicating the intention of the following code block.
do {: Marks the beginning of a do-while loop. The code inside the curly braces will be executed at least once before checking the loop condition.
printf("Input an integer (enter 0 to stop): ");: Displays a prompt asking the user to input an integer, with an additional instruction to enter 0 to stop.
scanf("%d", &num);: Reads the entered integer from the user and stores it in the variable num.
if (num > 0) {: Checks if the entered number is positive.
sum += num;: If the number is positive, it is added to the sum variable.
} else if (num < 0) {: If the number is negative, this block is executed.
printf("Negative integers are not considered. Ignored.\n");: Displays a message indicating that negative integers are not considered, and they are ignored.
} while (num != 0);: Specifies the loop condition. The loop continues as long as the user does not enter 0.
// Print the sum of positive integers: Comment indicating the intention of the following code block.
printf("Sum of positive integers: %d\n", sum);: Prints the sum of positive integers calculated during the loop.
return 0;: Indicates that the program executed successfully. The 0 here is typically used to indicate successful execution.
}: Marks the end of the main function.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to accept numbers until 0 is entered and then print the sum of even numbers only.
Write a C program to accept numbers until 0 is entered and count how many numbers were entered before 0.
Write a C program to accept numbers until 0 is entered and display the largest and smallest numbers entered.
Write a C program to accept numbers until 0 is entered and calculate the sum of the absolute values of all numbers.

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