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It may seem strange to say that a round basketball is facing in one direction or the other. However, every sprite has a front, back, top, and bottomeven in those cases where it is not visually obvious. (The orientation would be visually obvious if I were to use an animal for the sprite in place ofthe basketball. You can tell which direction the basketball is facing by observing the curved diagonal lines on the basketball.)

After you drag the blue block labeled point in direction into the center pane, you can click the arrow in the white box to expose the followingfour choices:

  • (90) right
  • (-90) left
  • (0) up
  • (180) down

As you can see, I selected the choice that causes the basketball to face to the right. As a result, when the user clicks the green flag, the basketballwill move to the origin and turn to face the right.

Handling mouse events on the basketball

Image 8 shows all of the code in the center pane that applies to the basketball.

Image 8. all of the code that applies to the basketball.

Missing image.
Image 8. All of the code that applies to the basketball.

The top script in Image 8 is another image of the script that was shown in Image 7 . At this point, we are interested in the behavior of the bottom script in Image 8 .

Behavior of the bottom script

The tan block labeled when Basketball clicked specifies that all of the actions produced by the blocks below that block will occur when the userclicks the basketball with the mouse. Furthermore, those actions will occur in top to bottom order.

The blue block labeled move 90 steps causes the basketball to move 90 steps forward (in the direction that it is facing) . Each step constitutes one unit in the Cartesian coordinate system. For example, if you were to change this value from 90 to 240, thatwould cause the basketball to move from the origin to the extreme right edge of the Stage.

The selection block

As I indicated earlier , the selection structure is sometimes referred to as a decision structure. In other words, this structure causes the program to select or make a decision between two alternatives. The pseudocode in Image 9 describes this process.

Image 9. pseudocode for a selection structure.

if a specified condition is true perform a specified actionotherwise (when the specified condition is not true) perform a different action
Image 9. Pseudocode for a selection structure.

Sometimes the second part of the selection process isn't needed. In other words, in some cases, if the specified condition is not true, there is norequirement to do anything at all. That is the case in this program.

Two independent decisions

This program makes two independent decisions shown by the pseudocode in Image 10 .

Image 10. two independent decisions.

if the basketball is touching the beach ball on the right turn around and face to the leftif the basketball is touching the beach ball on the left turn around and face to the right
Image 10. Two independent decisions.

These two decisions are implemented by the two tan blocks in Image 8 containing the word if .

The Control group Clicking the tan Control button shown at the upper left in Image 4 exposes a large number of programming blocks. Twoof them are used to create pure selection structures and one is used to create a combination of a loop structure and a selection structure.

Selection control structures available in Scratch

Clicking the tan Control button shown at the upper left in Image 4 exposes the blocks shown in Image 11 . The bottom two blocks can be used to create pure selection structures. The top block can be used to create acombination of a loop structure and a selection structure.

Questions & Answers

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
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
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.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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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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