Editing While loop (section)

==Overview==
The ''while'' construct consists of a block of code and a condition/expression.<ref name=":0">{{cite web|url=http://docs.oracle.com/javase/tutorial/java/nutsandbolts/while.html|title=The while and do-while Statements (The Java Tutorials > Learning the Java Language > Language Basics)|website=Dosc.oracle.com|access-date=2016-10-21}}</ref> The condition/expression is evaluated, and if the condition/expression is ''true'',<ref name=":0" /> the code within all of their following in the block is executed. This repeats until the condition/expression becomes [[False (logic)|false]]. Because the ''while'' loop checks the condition/expression before the block is executed, the control structure is often also known as a '''pre-test loop'''. Compare this with the [[do while loop|''do while'' loop]], which tests the condition/expression ''after'' the loop has executed.

For example, in the languages [[C (programming language)|C]], [[Java (programming language)|Java]], [[C Sharp (programming language)|C#]],<ref>{{cite web |url=http://msdn.microsoft.com/en-us/library/2aeyhxcd.aspx |title=while (C# reference)|website=Msdn.microsoft.com|access-date=2016-10-21}}</ref> [[Objective-C]], and [[C++]], (which [[Polyglot (computing)|use the same syntax]] in this case), the code fragment

<syntaxhighlight lang="c">
int x = 0;

while (x < 5) {
    printf ("x = %d\n", x);
    x++;
}
</syntaxhighlight>

first checks whether x is less than 5, which it is, so then the {loop body} is entered, where the ''printf'' function is run and x is incremented by 1. After completing all the statements in the loop body, the condition, (x < 5), is checked again, and the loop is executed again, this process repeating until the [[Variable (computer science)|variable]] x has the value 5.

It is possible, and in some cases desirable, for the condition to ''always'' evaluate to true, creating an [[infinite loop]]. When such a loop is created intentionally, there is usually another control structure (such as a [[Control flow|break]] statement) that controls termination of the loop.
For example:

<syntaxhighlight lang="c">
while (true) {
    // do complicated stuff
    if (someCondition)
        break;
    // more stuff
}
</syntaxhighlight>