Editing Do while loop (section)

{{Short description|Programming control flow statement}}
[[File:Do-while-loop-diagram.svg|thumb|upright|Do While loop flow diagram]]
{{Loop constructs}}<!-- DO NOT remove. Discuss navigation concept at [[Talk:Do while loop#Helpbox experiment]] -->

In many [[computer programming]] [[Programming language|languages]], a '''do while loop''' is a [[control flow]] [[Statement (computer science)|statement]] that executes a block of code and then either repeats the block or exits the loop depending on a given [[Boolean data type|boolean]] condition.

The ''do while'' construct consists of a process symbol and a condition. First the code within the block is executed. Then the condition is evaluated. If the condition is [[Truth|true]] the code within the block is executed again. This repeats until the condition becomes [[False (logic)|false]].

Do while loops check the condition after the block of code is executed. This control structure can be known as a '''post-test loop'''. This means the do-while loop is an exit-condition loop. However a [[while loop]] will test the condition before the code within the block is executed.

This means that the code is always executed first and then the expression or test condition is evaluated. This process is repeated as long as the expression evaluates to true. If the expression is false the loop terminates. A while loop sets the truth of a statement as a necessary condition for the code's execution. A do-while loop provides for the action's ongoing execution until the condition is no longer true.

It is possible and sometimes desirable for the condition to always evaluate to be true. This creates an [[infinite loop]]. When an infinite loop is created intentionally there is usually another control structure that allows termination of the loop. For example, a [[Control flow#Early exit from loops|break statement]] would allow termination of an infinite loop.

Some languages may use a different naming convention for this type of loop. For example, the [[Pascal programming language|Pascal]] and [[Lua (programming language)|Lua]] languages have a "''repeat until''" loop, which continues to run ''until'' the control expression is true and then terminates. In contrast a "while" loop runs ''while'' the control expression is true and terminates once the expression becomes false.