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assignment-s-04.c

Problem Statement

Write a function to check whether a number is prime or not. Use the same function to generate all prime numbers less than 100.

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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  • Recursion
  • Sorting (possible)
  • Iteration

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Source Code

#include <stdio.h>
#include <math.h>

int isPrime(int);

int main()
{
    int n, i;
    printf("Enter the number: ");
    scanf("%d", &n);
    if (isPrime(n))
    {
        printf("\nInput %d is a Prime Number.", n);
    }
    else
    {
        printf("\nInput %d is not a Prime Number.", n);
    }
    printf("\nPrime Numbers less than 100:");
    for (i = 1; i < 100; i++)
    {
        if (isPrime(i))
        {
            printf("  %d", i);
        }
    }
    return 0;
}

int isPrime(int n)
{
    if (n <= 1)
        return 0;
    if (n == 2)
        return 1;
    if (n % 2 == 0)
        return 0;

    int temp = (int)sqrt(n);
    int i;
    for (i = 3; i <= temp; i += 2)
    {
        if (n % i == 0)
        {
            return 0;
        }
    }
    return 1;
}

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 (assignment-s-04.c):

    #include <stdio.h>
    #include <math.h>

    int isPrime(int);

    int main()
    {
        int n, i;
        printf("Enter the number: ");
        scanf("%d", &n);
        if (isPrime(n))
        {
            printf("\nInput %d is a Prime Number.", n);
        }
        else
        {
            printf("\nInput %d is not a Prime Number.", n);
        }
        printf("\nPrime Numbers less than 100:");
        for (i = 1; i < 100; i++)
        {
            if (isPrime(i))
            {
                printf("  %d", i);
            }
        }
        return 0;
    }

    int isPrime(int n)
    {
        if (n <= 1)
            return 0;
        if (n == 2)
            return 1;
        if (n % 2 == 0)
            return 0;

        int temp = (int)sqrt(n);
        int i;
        for (i = 3; i <= temp; i += 2)
        {
            if (n % i == 0)
            {
                return 0;
            }
        }
        return 1;
    }