while, do-while and for control looping and are sometimes classified as iteration statements. A statement repeats until the controlling Booleanexpression evaluates to false.

A loop is a sequence of statements which is specified once but which may be carried out several times in succession. The code "inside" the loop is obeyed a specified number of times, or once for each of a collection of items, or until some condition is met.

In computer programming, a loop is a sequence of instruction s that is continually repeated until a certain condition is reached. Typically, a certain process is done, such as getting an item of data and changing it, and then some condition is checked such as whether a counter has reached a prescribed number. If it hasn't, the next instruction in the sequence is an instruction to return to the first instruction in the sequence and repeat the sequence. If the condition has been reached, the next instruction "falls through" to the next sequential instruction or branches outside the loop. A loop is a fundamental programming idea that is commonly used in writing programs.

In writing a computer program it is often necessary to repeat part of a program a number of times. One way to achieve repetition is to write out that part of the program as many times as it is needed. This method is very impractical since it produces a very lengthy computer program and the number of repetitions is not always known in advance.

A better way to repeat part of a program a number of times is to introduce a loop into the code.