Difference Between While And Do While in C Programming

Let us understand what’s exactly the difference between While loop and Do While loop in C programming language. Find out the while and do while comparison in tabular format with an example, syntax and explanation.

What is a Loop?

A loop is a set of instructions that executes itself until the final condition is met. These loops are very useful to perform numerous tasks in a very short set of code.

 

An If-Else block which can be used to compare 10 values and produce a specific output can be shortened to a great extent using loops.

Looping structures are an integral part of every programming language. There are different types of loops in C programming such as:

While Loop in C Programming

The While loop is one of the most used looping structures in C programming language after For loop. It is one of the easiest to implement.

A while loop is an entry controlled loop where the condition checking is performed before the program control moves within the while loop.

Let us first see the syntax of a While loop. Also, see this implementation of while loop in C programming here.

Syntax

So, before the program control moves to the statements which are to be executed, the while condition is checked.

If the condition evaluates to true, the program control executes the statements and optionally performs an increment or decrement operation and then again moves back to the condition checking.

As soon as the condition evaluates to false, the program control moves out of the while loop block and executes any other statements.

While loop in C programming with syntax, flowchart, algorithm, example, output and explanation

Note: The following C programs for comparison of while and do while loop is compiled with GNU GCC compiler with CodeLite IDE on Microsoft Windows 10 operating system.

C Program To Print Numbers using While Loop

Do While Loop in C Programming

A do-while loop is very similar to a while loop in C programming. The primary difference here is that the do while loop has an exit controlled condition.

Let us now see the syntax of the do-while loop, and this syntax will help you find out the difference between while and do while loop.

Syntax

   

The exit condition is checked after one set of iteration has been performed. Therefore, at least one iteration is performed in a do while loop irrespective of whether the condition is true or false.

If the condition is true, the program control goes back to the do block and performs the iteration again and this happens until the condition is met.

If the condition turns out to be false, the program control exits the do block, and executes the other statements below, if any.

Do While loop in C programming with syntax, flowchart, algorithm, example, output and explanation

C Program To Print Numbers using Do While Loop

Output

Difference Between While and Do While Loop in C Programming in Tabular Format with Example, Comparison and Output

Conclusion

If you try and compare both the set of codes above, you will notice that there is not much difference between while and do while loop.

The major difference is that the while loop has the condition at the starting point whereas the Do while loop has the condition at the end of the loop.

Also, if you notice a minor fact here, there is a semicolon at the end of the do while looping condition whereas it does not exists in case of the while loop.

The statements within the while loop will never execute if the while condition is false however in case of a do while loop the block statements are going to be executed at least once.

Difference Between While and Do While Loop in C Programming in Tabular Format

Sr. No.While LoopDo While Loop
1.The while loop is an entry condition looping structure.The do while loop is an exit condition looping structure.
2.The number of iterations depends on the condition mentioned in the while block.Irrespective of the condition mentioned in the do while block, there will a minimum of 1 iteration.
3.Syntax:
Syntax:
4.The block control condition is available at the starting point of the loop.The block control condition is available at the end point of the loop.

If you have any compilation errors or doubts about the difference between while and do while loop or the codes mentioned above, let us discuss in the comment section below.

   

Find more about While loop on Wikipedia.

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