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General background information

In an earlier module (see Resources ) , I told you that any programming logic problem could be solved using anappropriate combination of only three programming structures, none of which are complicated. The three structures are known generally as:

  • The sequence structure.
  • The selection or decision structure.
  • The loop, repetition, or iteration structure.

I explained the sequence and selection structures in earlier modules. I will concentrate on the loop structure in this and the next module.

Definite versus indefinite loops

Loop structures in programming fall into two broad categories:

  • Definite loops
  • Indefinite loops

There are numerous sub-categories within these broad categories. I will illustrate the difference between a definite loop and an indefinite loop with two real-world examples.

A definite loop example

Assume that you are confronted with a full box of cookies. Assume also that you have more self-control than most of us, and that you decide you can eatthree cookies, but no more than three, in order to keep your waistline under control. You might eat the three cookies using an algorithm something like thatshown in Image A .

Image a. a definite loop for eating cookies.

for count = 1 to 3 Take cookie from boxEat cookie Increase count by oneGo back to the test at the top of the loop Stop eating cookies
Image A. A definite loop for eating cookies.

Explanation of the definite loop

Being the self-controlled individual that you are, you would set your cookie limit to 3 and you would set count to 1. You would then test count to see if it is within the range from 1 to 3 inclusive. If so, you would take acookie from the box and eat it. Then you would increase the value of count by 1 and go back to the top of the loop.

Back at the top of the loop, you would once again test the value of count to determine if it is still within the range from 1 to 3 inclusive. If so, youwould repeat the process, getting and eating another cookie, increasing the value of count by 1, and going back to the top of the loop.

When you find that the value of count has advanced to 4, you would recognize that this is outside the range of 1 to 3 inclusive. As a result, youwould terminate the loop and stop eating cookies. Well done!

An indefinite loop example

Assume once again that you are confronted with the same full box of cookies. However, like many of us, you aren't blessed with a lot of self-control. In thatcase, you might eat cookies using the algorithm shown in Image B .

Image b. an indefinite loop for eating cookies.

Set the value of stillHungry to true while ((stillHungry is true) and (box is not empty))Take cookie from box Eat cookieIf I am no longer hungry Set stillHungry to falseGo back to the test at the top of the loop Stop eating cookies
Image B. An indefinite loop for eating cookies.

Explanation of the indefinite loop

Unfortunately, for many of us, as soon as we see the full box of cookies, our stillHungry variable gets set to true.

We begin the process by performing a test to determine if stillHungry is true and the box of cookies is not empty. If that test returns true, we take a cookie from the box and eat it. Then we perform another test. If weare no longer hungry at that point, we set our stillHungry variable to false and go back to test at the top of the loop. Otherwise, we allow our stillHungry variable to remain true.

Back at the top of the loop, we test again to determine if stillHungry is true, and the box of cookies is not empty. If the test returns true, we gothrough the process again, eating another cookie, etc.

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Teaching beginners to code. OpenStax CNX. May 27, 2013 Download for free at http://cnx.org/content/col11498/1.20
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