# 2.4 Functions  (Page 2/5)

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This function has the name cylinderVolume, and has two parameters, r and h, both with type double. It returns a value with the type double.

return statement

The return statement ends execution of the current function, and jumps back to where the function was called:

`return [expression];`

expression is evaluated and the result is given to the caller as the value of the function call. This return value is converted to the function's return type, if necessary.

A function can contain any number of return statements:

```// Return the smaller of two integer arguments. int min( int a, int b ){ if ( a<b ) return a; else return b;}```

The contents of this function block can also be expressed by the following single statement:

`return ( a<b ? a : b );`

The parentheses do not affect the behavior of the return statement. However, complex return expressions are often enclosed in parentheses for the sake of readability.

A return statement with no expression can only be used in a function of type void. In fact, such functions do not need to have a return statement at all. If no return statement is encountered in a function, the program flow returns to the caller when the end of the function block is reached.

## Usage of functions

The instruction to execute a function, the function call, consists of the function's name and the operator ( ). For example, the following statement calls the function maximum to compute the maximum of the matrix mat, which has r rows and c columns:

`maximum( r, c, mat );`

The program first allocates storage space for the parameters, then copies the argument values to the corresponding locations. Then the program jumps to the beginning of the function, and execution of the function begins with first variable definition or statement in the function block.

If the program reaches a return statement or the closing brace } of the function block, execution of the function ends, and the program jumps back to the calling function. If the program "falls off the end" of the function by reaching the closing brace, the value returned to the caller is undefined. For this reason, you must use a return statement to stop any function that does not have the type void. The value of the return expression is returned to the calling function.

## Scope of variables

One of the C language’s strengths is its flexibility in defining data storage. There are two aspects that can be controlled in C: scope and lifetime. Scope refers to the places in the code from which the variable can be accessed. Lifetime refers to the points in time at which the variable can be accessed.

Three scopes are available to the programmer:

• extern : This is the default for variables declared outside any function. The scope of variables with extern scope is all the code in the entire program.
• static : The scope of a variable declared static outside any function is the rest of the code in that source file. The scope of a variable declared static inside a function is the rest of the local block.
• auto : This is the default for variables declared inside a function. The scope of an auto variable is the rest of the local block.

how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Do somebody tell me a best nano engineering book for beginners?
what is fullerene does it is used to make bukky balls
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
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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 ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
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
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
how did you get the value of 2000N.What calculations are needed to arrive at it
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