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As a binary operator, the minus character causes its right operand to be subtracted from its left operand. For example, the third statement belowsubtracts the variable y from the variable x and assigns the result of the subtraction to the variable z . After the third statement is executed, the variable z contains the value 1.

int x = 6;

int y = 5;

int z = x - y;

The minus character as a unary operator

As a unary operator, the minus character causes the algebraic sign of the right operand to be changed. For example, the second statement belowcauses a value of -5 to be assigned to (stored in) the variable x .

int y = 5;

int x = -y;

Binary operators use infix notation

To keep you abreast of the current jargon, binary operators in Scratch always use infix notation. This means that the operator appears between its operands.

Some other programming languages have unary operators that use prefix notation and postfix notation. For prefix notation, the operator appears before (to the left of) its operand. For postfix notation, the operator appears after (to the right of) its operand.

General behavior of an operator

As a result of performing the specified action, an operator can be said to return a value (or evaluate to a value) of a given type. The type of value returned depends on the operator and the type of the operands.

To evaluate to a value: To evaluate to a value means that after the action is performed, the operator and its operands are effectively replacedin the expression by the value that is returned.

Operator categories

There are many different kinds of operators. Therefore, the easiest way to study them is to divide them into categories such as the following

  • arithmetic
  • relational
  • logical
  • bitwise
  • assignment

This module will concentrate on arithmetic operators. Future modules will deal with other kinds of operators.


In this module, I will present and explain a Scratch program named Arithmetic01 . This program illustrates the use of the following arithmetic operators (see Image 4 ):

  • + (addition)
  • - (subtraction)

Variables with the following names are created and displayed on the screen (see Image 5 ):

  • LeftOperand - has a slider
  • RightOperand - has a slider
  • Sum
  • Diff

In addition, a button is displayed on the screen.

The user adjusts the values of the LeftOperand and RightOperand variables with a pair of sliders. When the user clicks the button, the variablenamed Sum displays the sum of the values of the left and right operands. The variable named Diff displays the result of subtracting the right operand from the left operand.

Discussion and sample code

I'm going to walk you through the steps required to develop this program, being brief on those things that you already know about and being more verboseon the new material.

To begin with, Image 1 shows a reduced screen shot of the user interface.

Image 1. reduced screen shot of arithmetic01 in operation.

Missing image.
Image 1. Reduced screen shot of Arithmetic01 in operation.

I realize that Image 1 lacks detail due to the requirement to reduce the size of the screen shot for publication in this format, but there are someaspects of Image 1 that are worth noting. I will go from left to right in Image 1 making comments.

Questions & Answers

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
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.
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
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
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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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