Print All Prime Numbers in Range in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

#include <stdio.h>
int isPrime(int n) {
    if (n < 2) return 0;
    for (int i = 2; i*i <= n; i++)
        if (n % i == 0) return 0;
    return 1;
}
void printPrimes(int low, int high) {
    for (int i = low; i <= high; i++)
        if (isPrime(i)) printf("%d ", i);
}

C Output

Input: 10 to 20  
Output: 11 13 17 19

C++ Program

#include <iostream>
using namespace std;
bool isPrime(int n) {
    if (n < 2) return false;
    for (int i = 2; i*i <= n; i++)
        if (n % i == 0) return false;
    return true;
}
void printPrimes(int low, int high) {
    for (int i = low; i <= high; i++)
        if (isPrime(i)) cout << i << " ";
}

C++ Output

Input: 1 to 10  
Output: 2 3 5 7

JAVA Program

boolean isPrime(int n) {
    if (n < 2) return false;
    for (int i = 2; i*i <= n; i++)
        if (n % i == 0) return false;
    return true;
}
void printPrimes(int low, int high) {
    for (int i = low; i <= high; i++)
        if (isPrime(i)) System.out.print(i + " ");
}

JAVA Output

Input: 5 to 15  
Output: 5 7 11 13

Python Program

def is_prime(n):
    if n < 2: return False
    for i in range(2, int(n**0.5)+1):
        if n % i == 0: return False
    return True

def print_primes(low, high):
    for i in range(low, high+1):
        if is_prime(i):
            print(i, end=' ')

Python Output

Input: 20 to 30  
Output: 23 29

In-Depth Explanation

Example

Let's take the range 10 to 20. We test every number:

10 → not prime

11 → prime

12 → not prime

13 → prime

14,15,16,18,20 → not prime

17, 19 → prime

Final output: 11 13 17 19

The trick is testing whether each number has any divisor besides 1 and itself. We improve the test by stopping at the square root of the number.

Real-Life Analogy

Consider prime numbers as VIP party guests. Every guest (number) must pass through a check point (test for divisibility). Any guest with an unofficial point of entry (i.e., can be divided by any number except 1 and itself) is not permitted inside. Only the guests with precisely two points of entry are authentic — that's the prime club!

Another perspective: think of sieving a list of distinct objects (such as unusual coins). If it has no smaller factors (no duplicates, defects, or imperfections), it remains — analogous to primes in number theory.

Why It Matters

Knowing how to recognize and produce prime numbers is important in:

Cryptography (RSA encryption employs large primes)

Hashing and security algorithms

Efficient data structuring

Number theory challenges in mathematics and computer science

It also instructs you on the idea of loop optimization through minimizing unneeded iterations (e.g., up to √n).

What You Learn from This

You learn to:

Write and apply helper functions (isPrime())

Optimize code by applying math knowledge

Manipulate ranges, loops, and conditions

It also lays down a strong foundation for subsequent topics such as:

Sieve of Eratosthenes (for multiple primes)

Prime factorization

Modular arithmetic

This exercise makes you more proficient in thinking in checks and filters, a key problem-solving skill.

Interview Relevance and Actual Projects

This is a super frequent question in entry-level to intermediate interviews. It allows interviewers to assess:

Looping skills

Prime-check logic

Optimization thinking

Follow-up interview assignments can be:

Finding the Nth prime

Printing prime pairs

Optimizing for big ranges using sieve

Real-world applications:

Generating keys for encryption

Checking number properties

Random number generation in game dev

SEO-Optimized Explanation

Printing all the prime numbers in a provided range is a basic algorithm in competitive programming, number theory, and security applications. The program operates by testing each number for divisibility and printing only those which have exactly two different factors — 1 and themselves. This is a very important concept for the understanding of prime-based encryption, secure hashing, and math-intensive algorithms in competitive programming. Learning to identify all primes between two values through C, C++, Java, and Python assists in developing confidence in number reasoning, loop optimization, and mathematical thinking. Whether for preparing coding interview problems or creating core logic, this problem lays the foundation for more complex algorithms in programming.