<< Chapter < Page Chapter >> Page >

Sequential memory or combination random/sequential memory isn't very useful for most computer programs at the inner working level because access to eachparticular piece of data is slow. As a result, most modern computers have random access memory that is used for storage and retrieval of data by programs whilethey are running and disks that are used for long-term storage and retrieval of data that needs to be saved over longer periods of time.


As the computer program performs its operations in the prescribed order, it is often necessary for it to store intermediate results somewhere in itsmemory and to retrieve those results later for use in subsequent operations. The intermediate results are often stored in little chunks of memory that werefer to as variables .

Brief definition of a variable

The following definition is paraphrased from Wikipedia .

In computer programming, a variable is a storage location and an associated symbolic name (an identifier) that contains some known or unknown quantity or information -- a value.
The variable name is the usual way to reference the stored value; this separation of name and content allows the name to be used independently of the exact information it represents.
The value stored in the variable may change during program execution.

A physical analogy

We can think of random access memory as being analogous to a metal rack containing a large number of compartments. The compartments are all the samesize and are arranged in a regular grid of rows and columns.

Each compartment has a numeric address printed above it. No two compartments have the same numeric address. Each compartment also has a little slot intowhich you can insert a name or a label for the compartment. No two compartments can have the same name.

Although the analogy is not perfect, we can think of one of those compartments as being analogous to a variable.

Pretend that you are a computer program

Think of yourself as a computer program. You have the ability to create labels for each compartment (variable) . You have the ability to write values on little slips of paper and to put them into the compartments. You also have the abilityto read the values written on the little slips of paper and to use those values for some purpose. However, there are four rules that you must observe:

  • You may not remove a slip of paper from a compartment without replacing it by another slip of paper on which you have written a value.
  • You may not put a slip of paper in a compartment without removing the one already there.
  • You may not give the same label or name to two or more compartments.
  • You may not change a label once you have assigned it to a compartment.

Names versus addresses

Although each compartment in the physical memory in the computer has a numeric address, as a programmer using a high-level programming language such as Scratch, you usually don't need to be concerned about the numeric addresses of the compartments. (The compartments are often referred to as locations in memory.)

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
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
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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
Got questions? Join the online conversation and get instant answers!
Jobilize.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?