`luc031-logic.c`¶

Problem Statement

Write a program to enter numbers till the user wants. At the end it should display the count of positive, negative and zeros entered.

Metadata¶

Property	Detail
Author	Amit Dutta amitdutta4255@gmail.com
Date	12 Dec 2025
License	MIT License (See the LICENSE file for details)
Difficulty	Beginner (index: 3 / 10)

Concepts¶

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Iteration

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Source Code¶

#include <stdio.h>
#include <stdlib.h> // for strtol
#include <string.h> // for strcmp

// Maximum size of the input line
#define MAX_INPUT_LEN 15 

int main() {
    // Initialize counters
    int positive_count = 0;
    int negative_count = 0;
    int zero_count = 0;

    // Buffer to store the user's input as a string (e.g., "123", "-50", or "n")
    char input_buffer[MAX_INPUT_LEN];
    int number;

    printf("--- Number Analyzer ---\n");
    printf("Enter numbers one by one. Type 'n' and press Enter to finish.\n\n");

    // Loop until the user enters 'n'
    while (1) {
        printf("Enter number or 'n': ");

        // Read the entire line of input into the buffer
        if (fgets(input_buffer, MAX_INPUT_LEN, stdin) == NULL) {
            // Handle EOF (end of file) or reading error
            break;
        }

        // Remove the trailing newline character from the input_buffer
        // The last character will be '\n' if the input was shorter than MAX_INPUT_LEN
        size_t len = strlen(input_buffer);
        if (len > 0 && input_buffer[len - 1] == '\n') {
            input_buffer[len - 1] = '\0';
        }

        // 1. Check for the termination condition
        if (strcmp(input_buffer, "n") == 0) {
            printf("\n'n' received. Stopping input...\n");
            break; // Exit the while loop
        }

        // 2. Attempt to convert the input string to an integer
        // sscanf attempts to read the string according to the format "%d" (decimal integer)
        // It returns 1 if a number was successfully read.
        int conversions = sscanf(input_buffer, "%d", &number);

        if (conversions == 1) {
            // Conversion was successful, now check the number's sign
            if (number > 0) {
                positive_count++;
            } else if (number < 0) {
                negative_count++;
            } else {
                zero_count++;
            }
            printf("  -> Number recorded: %d\n", number);
        } else {
            // Conversion failed. The input was neither 'n' nor a valid integer.
            printf("  -> Invalid input. Please enter a valid number or 'n'.\n");
        }
    }

    // Display the final results
    printf("\n====================================\n");
    printf("   Analysis Complete\n");
    printf("====================================\n");
    printf("Positive numbers entered: %d\n", positive_count);
    printf("Negative numbers entered: %d\n", negative_count);
    printf("Zeroes entered:           %d\n", zero_count);
    printf("Total numbers recorded:   %d\n", positive_count + negative_count + zero_count);
    printf("====================================\n");

    return 0;
}

Explanation¶

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    You are explaining a C programming code to a beginner.

    STRICT RULES:

    - Only use the given code. Do NOT assume anything not present.

    - Do NOT add extra examples.

    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

    - Follow the exact format below. Do NOT change headings.

    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (luc031-logic.c):

    #include <stdio.h>
    #include <stdlib.h> // for strtol
    #include <string.h> // for strcmp

    // Maximum size of the input line
    #define MAX_INPUT_LEN 15 

    int main() {
        // Initialize counters
        int positive_count = 0;
        int negative_count = 0;
        int zero_count = 0;

        // Buffer to store the user's input as a string (e.g., "123", "-50", or "n")
        char input_buffer[MAX_INPUT_LEN];
        int number;

        printf("--- Number Analyzer ---\n");
        printf("Enter numbers one by one. Type 'n' and press Enter to finish.\n\n");

        // Loop until the user enters 'n'
        while (1) {
            printf("Enter number or 'n': ");

            // Read the entire line of input into the buffer
            if (fgets(input_buffer, MAX_INPUT_LEN, stdin) == NULL) {
                // Handle EOF (end of file) or reading error
                break;
            }

            // Remove the trailing newline character from the input_buffer
            // The last character will be '\n' if the input was shorter than MAX_INPUT_LEN
            size_t len = strlen(input_buffer);
            if (len > 0 && input_buffer[len - 1] == '\n') {
                input_buffer[len - 1] = '\0';
            }

            // 1. Check for the termination condition
            if (strcmp(input_buffer, "n") == 0) {
                printf("\n'n' received. Stopping input...\n");
                break; // Exit the while loop
            }

            // 2. Attempt to convert the input string to an integer
            // sscanf attempts to read the string according to the format "%d" (decimal integer)
            // It returns 1 if a number was successfully read.
            int conversions = sscanf(input_buffer, "%d", &number);

            if (conversions == 1) {
                // Conversion was successful, now check the number's sign
                if (number > 0) {
                    positive_count++;

    ... (truncated for brevity)

luc031-logic.c¶