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Eventually, either our stillHungry variable will be set to false, or the cookie box will become empty. At that point, the test will return false. Wewill terminate the loop and will stop eating cookies even though we might still be hungry for more cookies.

The while and for keywords

Most modern programming languages use the keywords while and for to implement loop structures such as this and you will see those keywords in useonce you get to Java, C++, C#, etc.

However, Scratch does not use those keywords to implement loops. Regardless, when I present pseudocode examples to explain Scratchprograms, I will continue to use while and for to get you accustomed to that terminology.


In this module, I will present and explain the following two Scratch programs:

  • ForLoop01 - This program illustrates the Scratch equivalent of a for loop (or something similar to a for loop) in other languages. In Scratch, it is called a repeat loop.
  • ForLoop02 - This program also illustrates the Scratch equivalent of a for loop in other languages. However, this program takes a different approach to specifying the number of times that the code in theloop is executed.

In addition, I will provide the specifications for a student-programming project for you to demonstrate your understanding of what you learned from thetwo programs listed above. In addition, this programming project will require you to do some independent research into the manner in which Scratch sprites cancommunicate with one another.

Discussion and sample code

The program named ForLoop01

This program illustrates the Scratch equivalent of a for loop (or something similar to a for loop) in other programming languages. In Scratch, it is called a repeat .

Why do I keep saying "something similar to a for loop?" The reason is that a for loop in other programming languages has many facets. Therepeat loop in Scratch is much more restricted than a for loop in those other languages.

This program places a cat sprite having two costumes on the stage. When the user clicks the green flag, code is executed that is equivalent to thepseudocode shown in Image C .

Image c. pseudocode for the program named forloop01.

Initialize cat position, orientation, and costume for(count = 0;count<24,count = count + 1){Cat moves ten steps forward. Cat waits 0.1 secondCat switches to costume #2 Cat turns 15 degreesCat waits 0.1 second Cat switches back to costume #1}//end for loop
Image C. Pseudocode for the program named ForLoop01.

Why set count to 0 ?

Most modern programming languages typically start counting with 0 instead of 1, but that is not necessarily the case with Scratch. You will learn more aboutthat when you get into Java, C++, C#, etc.

Purpose of the pseudocode

My purpose in providing the pseudocode is to help you better understand the Scratch code that follows. I am also preparing you for the use of otherprogramming languages later. I recommend that you compare the pseudocode with the Scratch code, and compareboth of them with what you see when you run the program.

What's new in this Scratch program?

This program contains several new code blocks that haven't been used in previous modules:

  • The switch costume block
  • The repeat block
  • The wait block

The only one of these blocks that I would put in the programming fundamentals category is the repeat block, and even the syntax of that block is quite a bit different from other modern programming languages.However, the other blocks are some of the things that cause Scratch programming to be fun, so I will use and explain such blocks as we go along.My only caution is that you should not expect to find those commands in other programming languages, at least not using the same syntax.

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
in a comparison of the stages of meiosis to the stage of mitosis, which stages are unique to meiosis and which stages have the same event in botg meiosis and mitosis
Leah 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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