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luc106.c

Problem Statement

Write a program to scan an 8-bit number and check whether its 3rd, 6th and 7th bit is on.

Metadata

Property Detail
Author Amit Dutta amitdutta4255@gmail.com
Date 08 Feb 2026
License MIT License (See the LICENSE file for details)
Difficulty Beginner (index: 1 / 10)

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Source Code

#include <stdio.h>
#include <stdlib.h>

int main()
{
    unsigned char num;

    printf("Enter an 8-bit integer (0-255): ");
    scanf("%hhu", &num);

    // Checking bits 3, 6, 7. 
    // Assuming 0-based indexing: 3rd bit is index 3 (value 8), 6th is index 6 (64), 7th is index 7 (128).

    unsigned char mask = (1 << 3) | (1 << 6) | (1 << 7);

    if ((num & mask) == mask)
        printf("Bits 3, 6, and 7 are ALL ON.\n");
    else
        printf("Bits 3, 6, and 7 are NOT all on.\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 (luc106.c):

    #include <stdio.h>
    #include <stdlib.h>

    int main()
    {
        unsigned char num;

        printf("Enter an 8-bit integer (0-255): ");
        scanf("%hhu", &num);

        // Checking bits 3, 6, 7. 
        // Assuming 0-based indexing: 3rd bit is index 3 (value 8), 6th is index 6 (64), 7th is index 7 (128).

        unsigned char mask = (1 << 3) | (1 << 6) | (1 << 7);

        if ((num & mask) == mask)
            printf("Bits 3, 6, and 7 are ALL ON.\n");
        else
            printf("Bits 3, 6, and 7 are NOT all on.\n");

        return 0;
    }