13.1: Iteration Control Structures
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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
.
[1]
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: While
count assigned zero While count < 5 Display "I love computers!" Increment count End
pseudocode: Do While
count assigned five Do Display "Blast off is soon!" Decrement count While count > zero
pseudocode: Repeat Until
count assigned five Repeat Display "Blast off is soon!" Decrement count Until count < one
pseudocode: For
For x starts at 0, x < 5, increment x Display "Are we having fun?" End