While vs Do While Loop: Difference and Comparison

Loops are among the most foundational building elements in programming. We use looping commands whenever we want to perform the same statement several times.

A loop is a set of instructions that repeats a statement depending on specific circumstances and then repeats the execution of a block or piece of code till the target is satisfied.

This article focuses on distinguishing between two widely used looping instructions, their use and sequential implementations, and includes a descriptive table and points of distinction.

Key Takeaways

1. A while loop executes a code block as long as a specified condition is true, whereas a do-while loop executes the code block at least once before checking the condition.
2. While loops test the condition before executing the code, do-while loops test the condition after executing the code.
3. Loops are suitable for situations where the condition must be met before the code is executed. In comparison, do-while loops are useful when the code must run at least once, regardless of the condition.

While vs Do While Loop

The difference between a while and a do-while loop is that the while loop executes a section of code until the statement is fulfilled, whereas the do-while loop executes all of the phrases inside the loop precisely once before assessing the loop’s requirement, and it runs at least once irrespective of whether the situation is fulfilled.

While loops are by far the most fundamental looping structures in coding and are used when the convergence rate is unknown.

This indicates that the while loop will execute a series of statements indefinitely until a specific condition is fulfilled.

The while loop executes a section of code until the statement is fulfilled, which means the loop will continue to run until the needed condition is fulfilled. This might happen after the first or thirtieth attempt as well.

Do while loop, on the other hand, is comparable to the while loop; however, it only examines the conditions after it has completed its commands, but the do-while loop constantly runs at least once.

Before assessing the loop’s precondition, it executes the lines inside the loop precisely once.

If the statement is fulfilled, control is sent to the phrase immediately after the while condition. If the condition becomes false, control is passed to the phrase immediately following that condition.

Comparison Table

Parameters of Comparison	While Loop	Do While Loop
Definition	Condition is evaluated first, and then the loop is initiated.	In this type of looping command, the loop is initiated first regardless of the command received, and then the result is evaluated.
Type	Entry controlled loop	Exit controlled loop
Iterations	If the conditions in the first command are false, the entire loop of repetition is eliminated.	In do-while-loop, the repeating text keeps looping even if the input command does not satisfy the conditions.
Application of Semicolon in Command	No semicolon is used as a part of the syntax itself.	Semicolon operation is used in the syntax.
Syntax	while ( condition) {statements; //body of loop}	do{.statements; // body of loop..} while( Condition );

What is a While Loop?

In Java and C/C++, while loop is a basic tool used by programmers. A while loop is common in operation in every programming language i.e. Java, C, and C++.

One commonly used basic function, the while loop, is simple and easy to execute. The while loop must be checked first, but if it is true, it repeats the loop until the default occurs. In a while loop, the predicate can be any binary value.

When an addition controls a non-zero value, the criterion is “true,” and if the result is zero, the criteria is labelled as “false”.

The functionality of binary unit-based codes is pretty much similar to a two-way switch; if the criterion value is a non-zero element, the loop initiates with the fed statements, whereas if the criterion value is zero, the loop moves to the next set of fed statements and start looping it accordingly.

The simplistic mechanism of a while-loop command makes it a widely used programming tool.

This is from the most basic looping structures in computing and programming, and they are used when the number of iterations is unknown.

The while loop executes a piece of code until the statement is fulfilled, which means the loop will continue to run until the needed condition is fulfilled.

The idea of iteration is linked to the desire to repeat an action. To control the loop’s execution, we pose a question, as we do with other control structures. When utilizing flowcharting, the term loop refers to the circular looping motion.

Although the initialization of the flag is not strictly part of the management structure, it is a required step before the loop can begin.

“While the phrase is true, take the following actions,” says the English version. In truth, this loops and is false, this iteration halts.

What is Do While Loop?

The do-while loop functions similarly to the while loop. However, it has one significant difference: the do-while-loop only studies the precondition after it has completed its commands, i.e. the first set of iterations, but it always runs at least once.

However, unlike the while loop, which can be ignored altogether if the expression is false the first time, the do-while loop ensures that the initially executed data set appears at least once, even if the conditions are satisfied.

This method is excellent when you don’t know the precise number of iterations and repetitions that the input can trigger.

The main body of the initial loop always appears before satisfying the preconditions, no matter if the expression or body has a null value (zero), as the latest programming languages like Java and C++ support zero insertion into the command slab.

If the satisfying criteria is a binary value or anything other than the null value, the repeating loop chooses and executes the required iteration set.

The do-while loop ensures that the body is getting properly executed at first, regardless of how much the condition is true or false on the first try.

But unlike the while loop, the precondition to ending the loop is not verified until the loop’s assertions have been completed. The do-while loop’s syntax is quite similar to the while loop’s, but it contains the semicolon function.

Main Differences Between While and Do While Loop

1. ‘While loop’ is also known as entry controlled loop, whereas ‘do while loop’ is called exit controlled loop.
2. ‘While loop’ has no semicolon in its syntax, whereas ‘do while loop’ has a semicolon.
3. In the ‘while loop’, the counter variable can be initialized before entering the loop body, but in the ‘do while loop’, it can be initialized both before and after entering the loop body.
4. The given condition is evaluated before the result in the ‘while loop’ whereas the given condition is evaluated after the first loop in the ‘do while loop’.
5. In the ‘while loop’, the controlling condition appears in the loop beginning, whereas it appears at last in the ‘do while loop’.

Last Updated : 11 June, 2023