Difference Between While and Do While Loop (With Table)

Loops are among the most foundational building elements in programming. Whenever we want to perform the same statement several times, we use looping commands. 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, as well as their use and sequential implementations, and includes a descriptive table and points of distinction.

While vs Do While Loop

The difference between while and 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 they 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, and if the condition becomes false, control is passed to the phrase immediately following that while condition.

Comparison Table Between While and Do While Loop

Parameters of ComparisonWhile LoopDo While Loop
DefinitionCondition 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.
TypeEntry controlled loopExit controlled loop
IterationsIf the conditions in the first command are false, the entire loop of repetition is eliminated.Whereas, in do-while-loop, the repeating text keeps looping even if the input command does not satisfy the conditions.
Application of Semicolon in CommandNo semicolon is used as a part of the syntax itself.Semicolon operation is used in the syntax.
Syntaxwhile ( condition) {statements; //body of loop}do{.statements; // body of loop..} while( Condition );

What is While Loop?

In Java and C/C++, while loop is a basic tool used by the programmers. A while loop is common in operation in every programming language i.e. Java, C, C++. One of the commonly used basic function, the while loop is simple and easy to execute. The while loop needs to 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 labeled 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 that happens.

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 in the same manner as the while loop although it has got one major difference which is; 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 makes sure that the initially executed data set makes its appearance at least once even if the conditions are satisfied. When you don’t know the precise number of iterations and repetition that the input can trigger, this method is excellent.

The main body of the initial loop always appears before satisfying the preconditions no matter if the expression or body has null value (zero) as the latest programming languages like Java and C++ support the insertion of zero 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 very 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 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 in its syntax.
  3. In the ‘while loop’, the counter variable can be initialized before entering the loop body but in ‘do while loop’ it can be initialized both before and after entering the loop body.
  4. Given condition is evaluated before result in ‘while loop’ whereas given condition is evaluated after the first loop in ‘do while loop’.
  5. In ‘while loop’ the controlling condition appears in the loop beginning whereas it appears at the last in ‘do while loop’.

Conclusion

The syntax and functionality of both loops are similar, with a few subtle variations that determine their usefulness. A while loop has a syntax that is quite similar to a do-while loop, but the key distinction is that the while loop assesses the circumstance too before running the commands, whereas the do-while loop runs the assertions but before analyzing the loop’s state. The while loop will not execute the assertions if the loop’s expression is false on the initial try.

References

https://www.tutorialspoint.com/cprogramming/c_do_while_loop.htm

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