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The test expression is within the parentheses, but this is not a function call. The parentheses are part of the control structure. Additionally, there is not a semicolon after the parenthesis following the expression.

An example

C++ source code: while

loop_response = 'y'; while (loop_response == 'y'){ cout<<"\nWhat is your age? "; cin>>age_user; cout<<"\nWhat is your friend's age? "; cin>>age_friend; cout>>"\nTogether your ages add up to: ";cout>>(age_user + age_friend); cout<<"\nDo you want to do it again? y or n "; cin>>loop_response; }

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The four attributes of a test before loop are present. The initialization of the flag. The test is the equality relational comparison of the value in the flag variable to the lower case character of y. The action part consists of the 6 lines that prompt for data and then displays the total of the two ages. The update of the flag is the displaying the question and getting the answer for the variable loop_response.

This type of loop control is called an event controlled loop. The flag updating is an event where someone decides if they want the loop to execute again.

Using indentation with the alignment of the loop actions and flag update is normal industry practice within the C++ community.

Infinite loops

At this point it's worth mentioning that good programming always provides for a method to insure that the loop question will eventually be false so that the loop will stop executing and the program continues with the next line of code.  However, if this does not happen then the program is in an infinite loop.  Infinite loops are a bad thing. Consider the following code:

C++ source code: infinite loop

loop_response = 'y'; while (loop_response == 'y'){ cout<<"\nWhat is your age? "; cin>>age_user; cout<<"\nWhat is your friend's age? "; cin>>age_friend; cout>>"\nTogether your ages add up to: "; cout>>(age_user + age_friend); }

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The programmer assigned a value to the flag before the loop which is correct. However, he forgot to update the flag. Every time the test expression is asked it will always be true. Thus, an infinite loop because the programmer did not provide a way to exit the loop (he forgot to update the flag). Consider the following code:

C++ source code: infinite loop

loop_response = 'y'; while (loop_response = 'y'){ cout<<"\nWhat is your age? "; cin>>age_user; cout<<"\nWhat is your friend's age? "; cin>>age_friend; cout>>"\nTogether your ages add up to: "; cout>>(age_user + age_friend); cout<<"\nDo you want to do it again? y or n "; cin>>loop_response; }

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No matter what the user replies during the flag update, the test expression does not do a relational comparison but does an assignment. It assigns 'y' to the variable and asks if 'y' is true? Since all non-zero values are treated as representing true within the Boolean concepts of the C++ programming language, the answer to the test expression is true. Viola, you have an infinite loop.

C++ source code: infinite loop

loop_response = 'y'; while (loop_response == 'y');{ cout<<"\nWhat is your age? "; cin>>age_user; cout<<"\nWhat is your friend's age? "; cin>>age_friend; cout>>"\nTogether your ages add up to: "; cout>>(age_user + age_friend); cout<<"\nDo you want to do it again? y or n "; cin>>loop_response; }

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Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Programming fundamentals - a modular structured approach using c++. OpenStax CNX. Jan 10, 2013 Download for free at http://cnx.org/content/col10621/1.22
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