Looping constructs (for, while, do-while)

Here’s a C code example demonstrating the three primary looping constructs: for, while, and do-while. Each loop here performs a similar task of counting from 1 to 5, but with a different syntax and approach.

#include <stdio.h>

int main() {
    int i;

    // Using a for loop to count from 1 to 5
    printf("For loop:\n");
    for (i = 1; i <= 5; i++) {
        printf("%d ", i);
    }
    printf("\n");

    // Using a while loop to count from 1 to 5
    printf("While loop:\n");
    i = 1;  // Initialize i before entering the loop
    while (i <= 5) {
        printf("%d ", i);
        i++;  // Increment i at the end of each iteration
    }
    printf("\n");

    // Using a do-while loop to count from 1 to 5
    printf("Do-while loop:\n");
    i = 1;  // Re-initialize i before entering the loop
    do {
        printf("%d ", i);
        i++;  // Increment i at the end of each iteration
    } while (i <= 5);
    printf("\n");

    return 0;
}

Explanation of Looping Constructs

1. For Loop

The for loop is ideal for a known number of iterations.

Syntax: for (initialization; condition; increment/decrement) { ... }

Example: for (i = 1; i <= 5; i++) { ... }

• i = 1 initializes the counter.
• i <= 5 is the loop condition; it runs as long as this condition is true.
• i++ increments i at the end of each loop iteration.

Output: The loop prints 1 2 3 4 5 and stops once i exceeds 5.

2. While Loop

The while loop is used when the number of iterations is not known in advance but depends on a condition.

Syntax: while (condition) { ... }

Example: while (i <= 5) { ... }

• i = 1 initializes the counter before the loop.
• i <= 5 is checked before each iteration, so the loop runs as long as this is true.
• i++ increments i at the end of each iteration.

Output: This loop also prints 1 2 3 4 5 and stops once i exceeds 5.

3. Do-While Loop

The do-while loop is similar to while but guarantees at least one iteration since the condition is evaluated after each loop.

Syntax: do { ... } while (condition);

Example: do { ... } while (i <= 5);

• i = 1 initializes the counter before the loop.
• The code inside the { ... } block executes at least once.
• i <= 5 is checked after each iteration, so the loop continues if the condition remains true.

Output: This loop also prints 1 2 3 4 5 and stops once i exceeds 5.

Summary of Looping Constructs

• for loop: Ideal when the number of iterations is fixed or known.
• while loop: Preferred when the loop depends on a condition that might vary dynamically, such as user input or program state.
• do-while loop: Guarantees at least one iteration, useful when you need the loop to run before checking the condition.

Each loop structure gives flexibility in controlling how many times a block of code executes, based on different types of conditions and requirements.