# 1.3 Scr0330: sequence, selection, and loop in scratch 2.0.  (Page 3/9)

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Also according to Wikipedia ,

"Pseudocode is an informal high-level description of the operating principle of a computer program or other algorithm. It uses the structural conventions of a programming language, but is intended for human reading rather than machine reading. Pseudocode typically omits details that are not essential for human understanding of the algorithm...
The purpose of using pseudocode is that it is easier for people to understand than conventional programming language code, and that it is anefficient and environment-independent description of the key principles of an algorithm."

## The sequence structure

We can describe the sequence structure using the pseudocode shown in Image 1 .

Thus, the general requirement for the sequence structure is that one or more actions may be performed in sequence after entry and before exit.

There may not be any branches or loops between the entry and the exit.

All actions must be taken in sequence.

## The action elements themselves may be structures

However, it is important to note that one or more of the action elements may themselves be sequence, selection, or loop structures.

If each of the structures that make up the sequence has only one entry point and one exit point, each such structure can be viewed as a single action elementin a sequence of actions.

The sequence structure is the simplest of the three, and there's not much more that I can say about it.

## The selection structure

The selection or decision structure can be described as shown in the pseudocode in Image 2 .

## Test a condition for true or false

Once again, there is only one entry point and one exit point.

The first thing that happens following entry is that some condition is tested for true or false .

The concept of something being true or false is commonly referred to as a boolean condition in computer programming (named after George Boole) .

If the condition is true, one or more actions are taken in sequence and control exits the structure.

If the condition is false, none , one or more different actions are taken in sequence and control exits the structure. (Note the inclusion of the word none here.)

## The action elements themselves may be structures

Once again, each of the action elements in the sequence may be another sequence, selection, or loop structure.

Eventually all of the actions for a chosen branch will be completed in sequence and control will exit the structure.

## Sometimes no action is required on false

It is often the case that no action is required when the test returns false. In that case, control simply exits the structure without performing any actions.

## The loop structure

The loop or iteration structure can be described as shown in the pseudocode in Image 3 .

As before, there is only one entry point and one exit point. Note that in this case, the exit point is not at the end of the pseudocode. Instead,it follows the test.

#### Questions & Answers

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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
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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