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Run the programs

I encourage you to use the information provided above to write and run these two programs. Experiment with the code, making changes, and observing theresults of your changes. Make certain that you can explain why your changes behave as they do.

Just for fun, see if you can add a drumbeat that keeps time as the cat walks.

I also encourage you to write the program described below.

Student programming project

Write a Scratch program named ForLoop03 . This program places a cat sprite, a slider variable, and a button on the stage as shown in Image K . The cat sprite has two costumes.

Image k. forloop03 output after clicking the green flag.

Missing image.
Image K. ForLoop03 output after clicking the green flag.

This program is an upgrade of the program named ForLoop02 , but is more complex than that program. In particular, this program uses the ability of onesprite (the button) to communicate with another sprite (the cat) by broadcasting and receiving messages.

You may have to do some online research to learn how to fire and handle broadcast events. Hint: See the bottom three blocks in the Events toolbox.

When the user clicks the button, this program behaves just like the program named ForLoop02 behaves when the user clicks the cat in that program. (Note, however, that the drawing of axes and lines was omitted from this program for simplicity.)

As in the previous program, this program executes its animation using a repeat block. Also as in the previous program, the number of times that the code in the repeat block is executed is specified by the current position of the slider.

Online version is available

A copy of this program has been posted online for your review (see Resources for the URL) . If you don't find the program using that URL, search the Scratch site for the usernamed dbal.


I began by providing a real-world example of the difference between a definite loop and an indefinite loop.

Then I presented and explained two Scratch programs that illustrate the Scratch equivalent of (or something similar to) a for loop in other programming languages. In Scratch, it is called a repeat loop. One of the programs caused a block of code to be executed a fixed number of times when the user clicked the greenflag. The other program caused a block of code to be executed a variable number of times when the user clicked a sprite.

I provided a brief introduction to the topic of animation and I explained the concept of costumes in Scratch. Both programs illustrate the use of costumes to implement crude animation that makes it appear that a cat sprite iswalking.

I also provided a student programming project.

What's next?

The next module will concentrate on other variations of Scratch loops.


General resources

Programs used in this series


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Scr0370: The repeat loop in Scratch 2.0
  • File: Scr0370.htm
  • Published: 05/18/13

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.


Questions & Answers

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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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