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Passing parameters

This process of providing information to a function when you call it is commonly referred to as passing parameters to the function. For the square-root function, you need to pass a parameter whose value is the value ofthe number for which you need the square root.

You call the built-in square root function in Scratch 2.0 by dragging the bottom block shown in Image B into the programming panel and selecting sqrt in the pull down list. You pass the parameter by entering a literal value or dragging a variable block into the white areathat contains the 9 character in Image B .

Returning values

A function or method will usually

  • Perform an action,
  • Send back an answer
  • Some combination of the two

Performing an action

You might think of performing an action as something like causing a Scratch sprite to move to the right and change color.

None of the Scratch 2.0 mathematical functions shown in Image C perform an action. One of the purposes of this module is to teach you how to create customblocks that do perform an action.

Sending back an answer

On the other hand, a function that is designed to calculate the square root of a number needs to be able to send the square-root value back to the programthat called the function. After all, it wouldn't be very useful if the function calculated the square root and then kept it a secret. The process of sendingback an answer is commonly referred to as returning a value .

All of the Scratch mathematical functions shown in Image C return a value.

It appears that there is no straightforward way for you to cause a custom block that you design to return a value. However, I will show you a workaroundfor that situation later.

Creating your own custom blocks

The best explanation that I have found for the mechanics of creating a custom block is contained in the document titled How Do I Use the New Blocks? on the MIT website. Go to that webpage and scroll down to the section titled Make Your Own Blocks . Follow the instructions that you find there to create your own custom blocks.

Sample programs

With that as an introduction, this section will present and explain two Scratch 2.0 programs built around custom blocks.

CustomBlockTest01

This is the simplest custom block that I could come up with that:

  • Receives an incoming parameter
  • Uses the value of that parameter to compute and return a value

This program contains the two scripts and a variable shown in Image D . These scripts are tied to the cat sprite.

Image d. program code for customblocktest01.

Missing image.
Image D. Program code for CustomBlockTest01.

A global variable

The variable named var shown on the left in Image D is a global variable. That means that it is accessible by any code in the program.

The custom block

The custom block named test is shown in the bottom script in Image D . When called, this block receives an incoming numeric parameter known locally as number1 . The code in the block multiplies that value by a factor of 2 and stores the resulting product in the variable named var , making it available to the code that called the custom block.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
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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