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Allowable variable names and lengths

Most programming languages have very specific requirements regarding the allowable characters for variable names. I suspect that this is also true ofScratch, but I haven't found that specification anywhere. You will probably be okay as long as you stick with letters, numbers, the underscore character"_", and the hyphen or minus sign "-".

It appears experimentally that the allowable length of the variable name is longer than you would ever want to use so length doesn't seem to be alimitation.

Many programming languages won't allow you to use a numeric character for the first character in a variable name, but that restriction doesn't seem to applyto Scratch. However, since you might later move up to more mainstream languages, you might want to avoid getting into the habit of using numeric characters asthe first character in variable names.

Meaningful variable names

When using Scratch and all other programming languages, you should strive to use variable names that are meaningful. My preference is to begin variable nameswith a lower-case letter, use multiple words in the name where appropriate, and separate the words using a format commonly called camelCase to cause the human eye to separate the words.

(The upper-case characters are analogous to the humps on a camel.)

Here is an example of the camelCase format:

aVariableName

Some people prefer the following format:

A_Variable_Name

I prefer the camelCase format because it is easier to type, requires fewer characters, takes less space, and in my opinion, is just as effective.

Writing the program

Generally speaking, programs are written in Scratch by:

  1. Selecting buttons in the upper-center of Image 1 to expose the programming blocks in the tool boxes associated with each of the categories listed earlier .
  2. Dragging programming blocks from the toolbox in Image 1 to the rightmost pane in Image 1 and snapping those blocks together in groups to form program scripts.
  3. Entering literal numeric values or dragging other blocks and dropping them into text fields with the same shapeto fill out the details of the program.

There are other steps involved in writing a complex program that I didn't include above, but we will get to them later in this collection of modules.Hopefully you already know the physical steps in writing a program as a result of working through some online tutorials.

Although Scratch 2.0 has some new features and a different screen layout, the general procedure for writing a program in Scratch 2.0 isessentially the same as the procedure for writing a program in Scratch 1.4. Thus, the older v1.4 tutorials are still very relevant.

As you can see in Image 1 , this program consists of three scripts in the rightmost pane. Each script contains onetan block and two orange blocks. We already know that orange blocks have to do with data or variables. As you can see from the colors on the left ends of the buttonsin Image 1 , tan blocks are related to Events .

Programming blocks in the Events category

Image 3 shows some of the programming blocks that are available in the Events category. (Scratch 1.4 had tools for the Events category and the Control category combined into a single toolbox.)

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
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
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Teaching beginners to code. OpenStax CNX. May 27, 2013 Download for free at http://cnx.org/content/col11498/1.20
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