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This is the action that is required whenever either of the touching blocks is true. In other words, whenever the basketball touches either of the beachballs, it must turn to facethe opposite direction and be prepared to move 90 steps in that direction the next time the user clicks the basketball.

An online version of this program 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.

Run the program

I encourage you to use the information provided above to write this program. Experiment with the code, making changes, and observing the results of yourchanges. Make certain that you can explain why your changes behave as they do.

Just for fun, use blocks from the purple Sound group and add some sound effects to your program.

I also encourage you to write the program described below.

Student programming project

Write a Scratch program named IfWithVar01 that produces the output shown in Image 13 when the user clicks the green flag. (Don't be concerned about matching the values in the x and y variables in Image 13 . )

Image 13. initial output from the program named ifwithvar01.

Missing image.
Image 13. Initial output from the program named IfWithVar01.

Orthogonal axes in Cartesian coordinates

When the user clicks the green flag, a DrawingPencil sprite draws a pair of orthogonal axes that intersect at the origin in the white Stage area.Make the horizontal axis extend from -200 to 200. Make the vertical axis extend from -100 to 100.

Draw a straight line to the location of the next mouse click

Each time the user clicks the mouse in the white Stage area (after the user has clicked the green flag) , a straight line is drawn from the current location of the DrawingPencil to the location where the mouse click occurred. Image 14 shows an example output after two mouse clicks.

Image 14. program output after having clicked twice in the stage area.

Missing image
Image 14. Program output after having clicked twice in the Stage area.

A sneak peek at the solution

In case you need to sneak a peek at the solution to this programming project, acopy 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 website for the usernamed dbal .)

Once you locate the project on the Scratch web site, you can execute it online.


I began by explaining structured programming, the sequence structure, the selection structure, and the loop structure. Then I presented andexplained a Scratch program that illustrates the selection structure. (The sequence structure is so simple that it doesn't require an explanation. The loop structure will be explained in a future module.) The program also illustrates the handling of mouse events and Cartesian coordinates.

Finally, I provided the specifications for a student-programming project for you to write to demonstrate your understanding of what you learned from thefirst program.

Copies of both programs have 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 .

What's next?

In the next module, I will teach you about arithmetic operators. In the two modules following that one, I will teach you about relational and logicaloperators and how to use those operators to write the conditional expressions used in selection and loop structures.



This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Scr0330: Sequence, Selection, and Loop in Scratch 2.0.
  • File: Scr0330.htm
  • Published: 05/11/13

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 freelyavailable on cnx.org and that it was made and published without my prior knowledge.

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


Questions & Answers

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.
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.
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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