Programming Fundamentals/Iteration Control Structures

Overview

In iteration control structures, a statement or block is executed until the program reaches a certain state, or operations have been applied to every element of a collection. This is usually expressed with keywords such as while, repeat, for, or do..until.

Discussion

The basic attribute of an iteration control structure is to be able to repeat some lines of code. The visual display of iteration creates a circular loop pattern when flowcharted, thus the word “loop” is associated with iteration control structures. Iteration can be accomplished with "test before" loops, "test after" loops, and counting loops. A question using Boolean concepts usually controls how often the loop will execute.

Pseudocode: Iteration (Repetition) Control Structures

While Loop

count assigned zero
While count < 5
    Display "I love computers!"
    Increment count
End

Do-While Loop

count assigned five
Do
    Display "Blast off is soon!"
    Decrement count
While count > zero

Repeat-Until Loop

count assigned five
Repeat
    Display "Blast off is soon!"
    Decrement count
Until count < one

For Loop

For x starts at 0, x < 5, increment x
    Display "Are we having fun?"
End

References

• cnx.org: Programming Fundamentals – A Modular Structured Approach using C++

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