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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

how can chip be made from sand
Eke Reply
is this allso about nanoscale material
are nano particles real
Missy Reply
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
where is the latest information on a no technology how can I find it
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
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
has a lot of application modern world
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
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
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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