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I am showing you the code in Image B for one purpose and one purpose only. The orange block with the label "forever if" no longer exists in Scratch v2.0.

Older programs that were written in v1.4 and published on the Scratch website were automatically converted to the Scratch v2.0 version, asshown in Image C when the website made the transition from v1.4 to v2.0.

Program code for the Scratch v2.0 version of the program named ForeverLoop01

The code for the Scratch v2.0 version of this program is shown in Image C . Note that this version replaces the forever if block with a forever block and embeds an if block in the forever block.

Except for the forever and next costume blocks, none of the blocks in Image C are new to this module.

Image c. program code for the scratch v2.0 version of the program named foreverloop01.

Missing image.
Image C. Program code for the Scratch v2.0 version of the program named ForeverLoop01.

The last block in the script

The bottom of the forever block is smooth. Nothing can be connected to the bottom of the block. Therefore, it must be the last block in the script that contains it.

The next costume block

An earlier module used a switch to costume block to cause the existing image of a sprite to be replaced by a different image. That blockrequires the programmer to specify the new costume by name each time a change in costume is needed.

The next costume block used in Image C is easier to use from a programming standpoint. As explained in the previous module, there is a list ofone or more costumes associated with each sprite. The next costume block causes the sprite to switch from the current costume to the next costume in the list. If the current costume is the last costume in the list, the blockcauses the sprite to switch back up to the first costume in the list.

The forever block

Code inside a forever block will run forever unless

  • some code inside the block causes it to stop running,
  • the user clicks the red stop button on the stage, or
  • the user shuts down the web page.

This is commonly referred to as an infinite loop .

An infinite loop is not always a bad thing. For example, many games run inside an infinite loop and that is also the case with this program. However,even though the program is running (after you click the green flag) , you don't see anything happening unless you press the space bar. Pressing thespace bar causes the cat to run around in a small circle.

Be careful and don't leave this program running in your browser unless that is your plan. You may find that while it is running, everything elseon your computer runs much more slowly than normal.

An if block

As you can see in Image C , an if block is embedded inside the forever block. During each iteration of the loop, a test is made to determine if the space key is pressed. Each time it performs the test and findsthe condition to be true, the code inside the if block is executed. If the condition is false, the code inside the if block is not executed.

When the condition is true

The condition is true if the space bar is pressed when the test is made. When the condition is found to be true, the sprite:

Questions & Answers

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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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
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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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