# 1.6 Scr0360: logical operators in scratch 2.0  (Page 3/7)

 Page 3 / 7

The range of each slider variable is set to -10 to 10.

## Event handlers

Three event handlers, shown as the bottom three scripts in the programming panel in Image A , are written to fire each time the button is clicked.

## Program operation

At runtime, the user adjusts the value of each of the slider variables.

When the user clicks the button, each event handler evaluates a relational-logical expression (an expression containing both relational and logical operators) . If the expression evaluates to true, a value of true is displayed in one of the bottom three variables on the stage in Image A . If the expression evaluates to false, a value of false is displayed in thatvariable.

## Meaningful variable names

In an earlier module, I told you that you should always strive to use meaningful variable names. At this point, you are probably thinking thatvariables named A , B , C , and D aren't very meaningful, and if so, your thinking is correct. However, there is a practical reason that I didn't use meaningful variable names in this case.

## Insufficient space

Really meaningful variable names usually require about five or more characters. However, I have limited display width in this presentation format. If I had used longer names for the variables in this program, theexpressions containing those variable names would have been quite long, and would have made it difficult for me to fit Image A into this presentation format.

You will note, however, that the bottom three variable names on the stage in Image A (also see the variables in the Data toolbox in Image A ) are meaningful. In fact they are probably more meaningful than would be thecase in Java because Java doesn't allow the space character, the left angle bracket character, or the "(" character to be included in a variable name.

## A truth table

According to Wikipedia:

"A truth table is a mathematical table used in logic -- specifically in connection withBoolean algebra, boolean functions, and propositional calculus -- to compute the functional values of logical expressions on each of their functionalarguments, that is, on each combination of values taken by their logical variables. In particular, truth tables can be used to tell whether a propositional expression is true for all legitimate input values, that is,logically valid."

## What does this mean?

The concept of a truth table is simpler than the above quotation might suggest. Image B is a simple truth table that shows the result of evaluating four logical expressions for all combinations of the values of two variables, A and B , where each variable can only take on the values of true and false .

## The and operation

If both A and B are true, then the expression (A and B) evaluates to true. Otherwise, it evaluates to false. Correspondingly, if (A and B) is true, then not(A and B) is false. Otherwise, it is true. Applying the not operator to a boolean value is often referred to as getting the complement of that value.

## The inclusive or operation

The operation that I am getting ready to discuss in known as an inclusive or operation. There is also an exclusive or operation that I won't discuss in this module. That will be a topic for a much more advanced module.

where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
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
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
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
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
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?
what is a peer
What is meant by 'nano scale'?
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 ?
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?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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