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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

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..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
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.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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.
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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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