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loops

summary

    This subchapter looks at loops.

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stub section

    This subchapter is a stub section. It will be filled in with instructional material later. For now it serves the purpose of a place holder for the order of instruction.

    Professors are invited to give feedback on both the proposed contents and the propsed order of this text book. Send commentary to Milo, PO Box 1361, Tustin, California, 92781, USA.

loops or repetition

    A loop or repetition is the act of repeating an action or actions. A lot of the power of computers is being able to do repetitive choices over and over (sometimes millions or more times).

    This is one of the most important and powerful features of a computer — the ability to repeatedly do something over and over in really large numbers of repetitions.

    The Iterative DO LOOP is perfomed the exact number of times the programmer specified.

    The DO WHILE loop is perfomed zero or more times.

    The DO UNTIL loop is perfomed at least once.

    The key difference between the DO WHILE loop and the DO UNTIL loop is that the condition test comes at the beginning of the DO WHILE loop and the condition test comes at the end of the DO UNTIL loop.

    The DO WHILE loop might never be performed (if the test condition fails before the first attempt to loop).

    The DO UNTIL loop will always be performed at least once (because the condition test occurs after the first pass of the loop).

Ada

JOVIAL

other

   “18. A program without a loop and a structured variable isn’t worth writing.” —Alan Perlis, Epigrams on Programming, ACM’s SIGPLAN Notices Volume 17, No. 9, September 1982, pages 7-13

chapter contents

• iterative (do/for) loop
• counters, increment, and decrement
• while loop
• until loop
• early exit
• branching

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