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

These two decisions are implemented by the two light tan blocks in Image 8 containing the word if . (From this point forward, I won't distinguish between dark tan and light tan.)

Clicking the tan Control button shown at the upper center in Image 4 exposes a large number of programming blocks. Twoof them are used to create pure selection structures (if-then and if-then-else) and one is used to create a combination of a loop structure and a selection structure (repeat-until).

Control structures available in Scratch

Clicking the tan Control button shown at the upper center in Image 4 exposes the blocks shown in Image 11 . As mentioned above, two of the blocks can be used tocreate pure selection structures and one can be used to create a combination of a loop structure and a selection structure. The other blocksserve other purposes.

Selection structures are created by dragging the selection blocks into the rightmost panel in order to apply them to a particularsprite.

Image 11. control structures available in scratch.

Missing image.
Image 11. Control structures available in Scratch.

How do the two if blocks differ?

The if-then-else block in Image 11 is used to select between two specific actions (or two sequences of actions) . The if-then block is used when there is only one action (or one sequence of actions) and you need to decide whether to take that action or not.

That latter case describes the situation in this program. If the basketball is touching a beachball, a specific action is required.If the basketball is not touching a beachball, no specific action is required.

Specifying the condition on which the decision will be based

Note the empty darker depressed area in some of the blocks shown in Image 11 (the rectangles with the pointed ends) . In order to use these blocks, you must drop another block having the same shape into the depressedarea. The block that you drop into that area must specify the condition that will be used to make the decision.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
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..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
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.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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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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