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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

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
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
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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