<< Chapter < Page Chapter >> Page >

Six blocks have the correct shape

As you can see in Image 4 , there are six blocks of the correct shape exposed by clicking the Operators button. Those blocks are identified as follows:

<(less than) = (equal to)>(greater than) andor not

We will refer to the first three blocks above as relational operators . (They are used to evaluate the relationship between two values.) We will refer to the other three blocks in the above list as logical operators , and will deal with them in a future module.

Relational operators in other languages

Many other modern programming languages also include the following three relational operators:

>= (greater than or equal)<= (less than or equal) != (not equal)

Although these operators are a great convenience, they are not essential. We can get by with only the three that are provided by Scratch.

Also, in many other programming languages, a pair of equal characters (==) is used for the equal to operator instead of the single equal character (=) used in Scratch.

Three steps at once

Image 5 shows the result of having taken three more steps in the development of the program:

  1. I dragged the green less than (indicated by a left angle bracket) block and dropped it into the pocket immediately to the right of the word if .
  2. I dragged the orange block labeled set...to for the variable named LessThan and inserted it immediately below the word if . I also set its literal value to 1.
  3. I dragged another copy of the orange block labeled set...to for the variable named LessThan and inserted it immediately below the word else . I left its literal value as the default value of zero.

Image 5. intermediate stage in construction of if-else script.

Missing image
Image 5. Intermediate stage in construction of if-else script.

Still need to complete the conditional clause

The script in Image 5 includes the action to be taken if the relational expression following the word if evaluates to true. It also includes the action to be taken if therelational expression evaluates to false. (This relational expression is often referred to as a conditional clause.) .

However, we still haven't completed the conditional clause in Image 5 . We don't want to test for the relationship between theliteral values blank and blank as shown in Image 5 . Instead we want to test the relationship between the values of the variablesnamed LeftOperand and RightOperand as shown in the corresponding script in Image 2 .

Complete the relational expression

The next and final step for constructing this script is to:

  • Click the Variables button to expose the variables as shown in Image 1 .
  • Drag the block for the variable named LeftOperand and drop it in the white box immediately to the left of the left angle bracket operator in Image 5 .
  • Drag the block for the variable named RightOperand and drop it in the white box immediately to the right of the left angle bracket operator in Image 5 .

Once we do that, we will have finished the construction of the second script from the top in Image 2 .

Completing the program

Following that, we need to go through essentially the same process to construct the bottom two scripts in Image 2 , using the other two relational operators in Image 4 along with the variables named LeftOperand and RightOperand .

Questions & Answers

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
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Berger describes sociologists as concerned with
Mueller Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Teaching beginners to code. OpenStax CNX. May 27, 2013 Download for free at http://cnx.org/content/col11498/1.20
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Teaching beginners to code' conversation and receive update notifications?

Ask