C Exercises: Find the prime numbers within a range of numbers

C For Loop: Exercise-34 with Solution

Write a program in C to find the prime numbers within a range of numbers.

The program should prompt the user to input the lower and upper bounds of the range. It will then check each number in this range to determine if it is prime, and display all the prime numbers found within these limits.

Sample Solution:

C Code:

#include <stdio.h> // Include the standard input/output header file.

void main(){
    int num,i,ctr,stno,enno; // Declare variables for the number, loop counters, and range.

    printf("Input starting number of range: "); // Prompt the user to input the starting number of the range.
    scanf("%d",&stno); // Read the input from the user.

    printf("Input ending number of range : "); // Prompt the user to input the ending number of the range.
    scanf("%d",&enno); // Read the input from the user.

    printf("The prime numbers between %d and %d are : \n",stno,enno); // Print the message indicating the range.

    for(num = stno; num <= enno; num++) // Loop through the numbers in the specified range.
    {
        ctr = 0; // Initialize the counter.

        for(i = 2; i <= num/2; i++) // Loop through possible divisors.
        {
            if(num % i == 0) // If a divisor is found...
            {
                ctr++; // ...increment the counter.
                break; // Exit the loop.
            }
        }

        if(ctr == 0 && num != 1) // If no divisors were found and the number is not 1...
            printf("%d ",num); // ...print the prime number.
    }
    printf("\n");  // Move to the next line after printing all prime numbers.
}

Output:

Input starting number of range: 1                                                                             
Input ending number of range : 50                                                                             
The prime numbers between 1 and 50 are :                                                                      
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47  

Flowchart:

C Programming Code Editor:

Previous: Write a C program to display Pascal's triangle
Next: Write a program in C to display the first n terms of Fibonacci series.