While

While is a keyword in many programming languages that is used to create a control flow structure known as a loop. The while loop is a fundamental concept in computer programming, and is used to repeatedly execute a block of code as long as a certain condition is true.

Syntax

The syntax of the while loop varies between different programming languages, but the general structure is the same. A condition is specified in parentheses after the while keyword, and the code to be executed is enclosed in braces. For example, in the C programming language, the syntax would look like this:

``` while (condition) {

   // code to be executed

} ```

Usage

The while loop is used when a programmer wants to repeat a block of code an unknown number of times until a certain condition is met. This could be, for example, when reading data from a file until the end of the file is reached, or when asking for user input until valid input is received.

Comparison with other loops

While loops are similar to for loops and do while loops. The main difference is that the condition in a while loop is checked before the loop is executed, whereas in a do while loop, the condition is checked after the loop is executed. This means that a do while loop will always execute at least once, whereas a while loop may not execute at all if the condition is not met initially.

See also

• Control flow
• Loop
• For loop
• Do while loop