Iterative control allows a part of the program to be repeated a number of times.
The word iteration is used instead of the word repetition as repetition implies that a sequence of actions controlled by the loop will be executed at least once, whilst iteration implies that the actions may not be executed at all. There are two forms of iteration. Definite iteration is where the number of times a part of the program will be executed can be determined by the program immediately before the iterative structure is encountered. This includes the situation where the number of times can be determined from the specification. Indefinite iteration is where the number of times cannot be determined until the iterative structure is encountered.