Definition   ITERATION is the act of repeating the construct,  or a slight variation on a construct,  again and again in some controlled fashion.

Remark
There are three main mechanisms of iteration:

• ``while''
  
• ``for''
  
• recursion
  

Definition   A WHILE STATEMENT is a repetition construct in which an action will continue to be repeated if some condition is true.

Definition   A COUNTER CONTROL LOOP is a repetition construct which is characterized by before-hand knowledge of how many times the instruction block is to be run.

Remark
Counter control loops are controlled by a counter which governs the behavior of the loop.

Definition     A DATA CONTROL LOOP is a repetition construct which is governed by ``metadata'' accompanying the data being processed.   The ``metadata'' is the input which breaks the loop.

Definition     INCREMENTAL PROGRAMMING is a programming methodology wherein one develops a program by writing a sequence of programs with the following properties:

1. The first program in the sequence performs some essentially trivial task,  but one which is fundamental to completion of the ultimate task.
   
2. The last program in the sequence performs the task of ultimate interest.
   
3. Each successor program performs a task only marginally more elaborate than its predessor.