C While Loop Examples

Welcome to The Coding College, where we simplify coding concepts for every learner! In this post, we’ll delve into practical examples of the while loop in C programming, showcasing how this essential construct is used to handle repetitive tasks effectively.

What is a while Loop?

The while loop in C allows you to execute a block of code repeatedly as long as a specified condition evaluates to true. It is especially useful when the number of iterations is not known beforehand.

Syntax

while (condition) {
    // Code to execute
}
  • Condition: Evaluated before each iteration.
  • Code Block: Executes only if the condition is true.
  • Loop Exit: If the condition becomes false, the loop stops.

Example 1: Print Numbers from 1 to 10

#include <stdio.h>

int main() {
    int i = 1;

    while (i <= 10) {
        printf("%d\n", i);
        i++;
    }

    return 0;
}

Output:

1  
2  
3  
4  
5  
6  
7  
8  
9  
10

Explanation:

  • Initialization: i is initialized to 1.
  • Condition: The loop runs as long as i is less than or equal to 10.
  • Update: i++ increments i in each iteration.

Example 2: Sum of Natural Numbers

#include <stdio.h>

int main() {
    int n, sum = 0, i = 1;

    printf("Enter a number: ");
    scanf("%d", &n);

    while (i <= n) {
        sum += i;  // Add i to sum
        i++;
    }

    printf("Sum of first %d natural numbers is: %d\n", n, sum);

    return 0;
}

Output:

Enter a number: 5  
Sum of first 5 natural numbers is: 15

Explanation:

  • The loop adds each number from 1 to n to sum.

Example 3: Reverse a Number

#include <stdio.h>

int main() {
    int num, reverse = 0;

    printf("Enter a number: ");
    scanf("%d", &num);

    while (num != 0) {
        reverse = reverse * 10 + num % 10;
        num /= 10;
    }

    printf("Reversed number is: %d\n", reverse);

    return 0;
}

Output:

Enter a number: 1234  
Reversed number is: 4321

Explanation:

  • The loop extracts the last digit using % 10 and shifts it to form the reversed number.

Example 4: Factorial of a Number

#include <stdio.h>

int main() {
    int n, i = 1;
    unsigned long long factorial = 1;

    printf("Enter a number: ");
    scanf("%d", &n);

    while (i <= n) {
        factorial *= i;
        i++;
    }

    printf("Factorial of %d is: %llu\n", n, factorial);

    return 0;
}

Output:

Enter a number: 5  
Factorial of 5 is: 120

Explanation:

  • The loop calculates the product of all integers from 1 to n.

Example 5: Infinite Loop

#include <stdio.h>

int main() {
    int i = 1;

    while (1) {  // Infinite loop
        printf("%d\n", i);
        i++;

        if (i > 10) {  // Exit condition
            break;
        }
    }

    return 0;
}

Output:

1  
2  
3  
...  
10

Explanation:

  • The break statement is used to exit the infinite loop when i exceeds 10.

Use Cases for while Loops

  • User Input Validation: Ensure the input meets certain criteria.
  • Menu-Driven Programs: Keep displaying a menu until the user chooses to exit.
  • Processing Data: Perform operations on data until a condition is met.

Advanced Example: Fibonacci Sequence

#include <stdio.h>

int main() {
    int n, t1 = 0, t2 = 1, nextTerm;

    printf("Enter the number of terms: ");
    scanf("%d", &n);

    printf("Fibonacci Sequence: ");

    int i = 1;
    while (i <= n) {
        printf("%d, ", t1);
        nextTerm = t1 + t2;
        t1 = t2;
        t2 = nextTerm;
        i++;
    }

    return 0;
}

Output:

Enter the number of terms: 5  
Fibonacci Sequence: 0, 1, 1, 2, 3,

Best Practices

  1. Avoid Infinite Loops: Always ensure the loop has a valid termination condition.
  2. Keep It Simple: Don’t overcomplicate the logic inside the loop.
  3. Optimize Updates: Ensure variables in the condition are updated correctly within the loop.

Conclusion

The while loop in C is a versatile tool that enables programmers to tackle a wide variety of tasks, from simple number printing to complex operations like reversing a number or generating a Fibonacci sequence. By mastering its use, you’ll elevate your coding efficiency and problem-solving skills.

Leave a Comment