Sum User-Entered Numbers in C

This program keeps accepting integers and adds them to a running total. A sentinel value tells the loop when to stop.

Sum Values Until 0 Is Entered Top ↑

#include <stdio.h>

int main(void) {
    int sum = 0;
    int value;

    while (1) {
        printf("Enter a number (0 to stop): ");

        if (scanf("%d", &value) != 1) {
            printf("Invalid input.\n");
            return 1;
        }

        if (value == 0) {
            break;
        }

        sum += value;
    }

    printf("Sum of the entered numbers: %d\n", sum);
    return 0;
}

Sample output

Enter a number (0 to stop): 4
Enter a number (0 to stop): 5
Enter a number (0 to stop): 7
Enter a number (0 to stop): 0
Sum of the entered numbers: 16

Allow 0 and Stop on a Negative Number Top ↑

When zero is a valid value, choose a different sentinel. Here, any negative number stops the loop and is not included in the sum.

#include <stdio.h>

int main(void) {
    int sum = 0;
    int value;

    while (1) {
        printf("Enter a non-negative number (negative to stop): ");

        if (scanf("%d", &value) != 1) {
            printf("Invalid input.\n");
            return 1;
        }

        if (value < 0) {
            break;
        }

        sum += value;
    }

    printf("Sum of the entered numbers: %d\n", sum);
    return 0;
}

Display the Highest Entered Number Too Top ↑

#include <stdio.h>

int main(void) {
    int sum = 0;
    int value;
    int highest = 0;
    int has_value = 0;

    while (1) {
        printf("Enter a non-negative number (negative to stop): ");

        if (scanf("%d", &value) != 1) {
            printf("Invalid input.\n");
            return 1;
        }

        if (value < 0) {
            break;
        }

        sum += value;

        if (!has_value || value > highest) {
            highest = value;
            has_value = 1;
        }
    }

    printf("Sum: %d\n", sum);

    if (has_value) {
        printf("Highest number: %d\n", highest);
    } else {
        printf("No numbers were entered.\n");
    }

    return 0;
}

Sum a Fixed Number of Inputs Top ↑

#include <stdio.h>

int main(void) {
    int count;
    int sum = 0;

    printf("How many numbers do you want to add? ");
    if (scanf("%d", &count) != 1 || count < 0) {
        printf("Enter a valid non-negative count.\n");
        return 1;
    }

    for (int i = 1; i <= count; i++) {
        int value;

        printf("Enter number %d: ", i);
        if (scanf("%d", &value) != 1) {
            printf("Invalid input.\n");
            return 1;
        }

        sum += value;
    }

    printf("The sum is: %d\n", sum);
    return 0;
}

Sum the Elements of an Array Top ↑

#include <stdio.h>

int main(void) {
    int values[] = {10, 20, 30, 40, 50};
    size_t count = sizeof values / sizeof values[0];
    int sum = 0;

    for (size_t i = 0; i < count; i++) {
        sum += values[i];
    }

    printf("The sum of the array elements is: %d\n", sum);
    return 0;
}

Output

The sum of the array elements is: 150

See also while loops, arrays, and sum of digits.

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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