Difference Between While and Do While Loop in C, C++ and Java

For any programmer, knowing the nuances of loops is like a rite of passage. Your understanding of loop forms can make or break your code's logic and is the key to mastering control flow in languages such as C, C++, and Java. This blog explores the Difference Between While and Do while loops, two fundamental loop categories, illustrating their distinctions with syntaxes and examples. Read on and streamline your path in the world of Programming! 

Table of Contents

1) What are Loops? 

2) What is While Loop? 

3) What is Do While Loop? 

4) Difference Between While and Do While Loop 

5) Conclusion 

What are Loops? 

Loops are essential control structures in Programming Languages that allow for repeating a block of code based on a specified condition. There are three primary types of loops: 

1) The "for" loop is used when you know how many iterations are needed. 

2) The "while" loop repeats if a given condition is true. 

The "do while" loop guarantees at least one execution of the loop body before checking the condition. Loops are fundamental for automating repetitive tasks, iterating through data structures such as arrays, implementing conditional logic, and creating interactive programs. This makes them a critical tool for efficient and concise coding. 

What is While Loop? 

A while loop is called an entry-controlled loop. In this loop, you can check the condition at the start of the loop structure. A code block will run until the condition is true, and if the condition is false, the loop gets terminated or ended. If the condition continues to be true, we call it an infinite loop. 

Syntax of While Loop 

The syntax of While loop is as follows:
 

Working of While Loop 

The working of While loop involves: 

a) Initialisation of Control Variable 

b) Condition Check
 

Example of While Loop 

Here’s an example of While loop: 

Let’s examine what happens here: 

a) Initialisation: int counter = 1; initialises the counter variable. 

b) Condition: while (counter <= 6) checks if the counter is less than or equal to 6. 

c) Execution: Inside the loop, printf("Counter: %dn", counter); prints the current value of the counter. 

d) Update: counter++; increments the counter by 1. 

e) The loop repeats until the counter exceeds 6, at which point the loop ends. 

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What is Do While Loop? 

The do while is also called an exit-controlled Loop because you can check the condition at the end of the loop structure in this loop. It is similar to the while loop, except the condition is checked in the last. If the condition is not true, a code block will run once. If the condition is true, it will return to the loop body. If the condition is false, control is removed from the loop, and the loop is terminated. 

Syntax of Do While Loop
 

Working of Do While Loop 

Working of Do while loop involves: 

a) Initialisation of control variable 

b) Loop Body gets executed first; then the condition is evaluated
 

Example of Do While Loop 

Here’s an example of Do while loop:

a) Initialisation: int counter = 1; initialises the counter variable. 

b) Execution: The code inside the do block executes at least once, regardless of the condition. printf("Counter: %dn", counter); prints the current value of the counter. 

c) Update: counter++; increments the counter by 1. 

d) Condition: After executing the block, the while (counter <= 6); checks if the counter is less than or equal to 6. If true, the loop repeats; otherwise, it exits. 

This loop will print the counter values from 1 to 6. 

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Difference Between While and Do While Loop 

While do while loops are commonly used looping statements in C, C++ and Java Programming Languages, both loops allow repetitive execution of a code block as long as the given condition remains true. The key difference between a while and a do-whole loop lies in their control flow mechanism and the order of condition evaluation. 

Here’s a summary of the main differences between while and do while loop: 

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Conclusion 

Understanding the differences between while and do while loop in C, C++ and Java enables you to write more precise and effective code. By knowing when each loop executes and how conditions are evaluated, you can control your program's flow better. Having a firm grasp of these distinctions is essential for laying down the fundamentals for your programming career. 

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