<< Chapter < Page Chapter >> Page >

Instead, you can think about the compartments and refer to them in terms of their names. (Names are easier for most people to remember and understand than numeric addresses.) Keep in mind, however, that computer memory locations don't really have names. Deep inside the computer program, the namesthat you use to identify compartments in memory are cross-referenced to memory addresses. At the lowest level, the program works with memory addresses insteadof names.

Execute an algorithm

A computer program always executes some sort of procedure or algorithm. The algorithm may be very simple (such as how to make a peanut butter sandwich) , or it may be very complex as would be the case for a spreadsheet program. As theprogram executes the algorithm, it uses the random access memory to store and retrieve the data that is needed to execute the algorithm.

Declaring a variable

In Scratch, it is necessary to establish the name of a variable before you can use it. (That is not the case in some programming languages such as Python.)

In programmer jargon, this is referred to as declaring a variable . The process of declaring a variable causes memory to be set aside to contain avalue, and causes that chunk of memory to be given a name. That name can be used later to refer to the value stored in that chunk of memory.

Some programming languages, (not including Scratch), require that the variable declaration also specify the type of data that will be storedin a variable.

Case sensitivity

The name of a variable is case sensitive in Scratch (but the name may not be case sensitive in other programming languages) . In other words, the name avariable is not the same as the name aVariable in case-sensitive programming languages. If both names were used in the sameprogram, they would refer to two different variables.

Use names to access values

Variables have names like price , cost , and markup . The names of the variables give us easy access to the values stored in the variables.

Some operations cause the value of a variable to change while other operations simply access the value without changing it.

Storing and retrieving

As the program executes, the values stored in variables can be replaced by other values. In that way, the values of the variables can change asthe program executes. (In other words, the value of a variable can vary over time.)

It is also possible to retrieve the value stored in a variable without modifying it. In that way, the values of variables can be used to evaluateexpressions without modifying those values.

Literals

Where does data originate ?

The data used by a computer program can originate from a variety of sources. For example, it can be entered from the keyboard. It can be read from a diskfile. It can be downloaded from a web site, etc.

Hard coded data

The data values can also be coded into the program when the program is written. In this case, we would call it a literal or a literal value .

A value coded into the program

That is just about all there is to understanding literals. There are some special rules that come into play in certain situations, and I will discussthose rules at the appropriate points in time. For now, just remember that a literal is a value that is coded into the program when the program is written.

Questions & Answers

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
Do somebody tell me a best nano engineering book for beginners?
s. Reply
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
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
types of nano material
abeetha Reply
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.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Teaching beginners to code. OpenStax CNX. May 27, 2013 Download for free at http://cnx.org/content/col11498/1.20
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Teaching beginners to code' conversation and receive update notifications?

Ask