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Four variables

The leftmost panel shows that four variables have been created. Because you can't read the names of those variables, I will list them here:

  • LeftOperand
  • RightOperand
  • Sum
  • Diff

You can barely see that the checkboxes next to all four variables have been checked. As you learned in an earlier module, checking this box causes avariable to be displayed in the white Stage area on the right. Thus you can see all four variables being displayed in the upper left corner of theStage.

A button

Skipping to the area immediately below the Stage, you can (almost) see that a button has been added to the program. That button has been selected in Image 1 , making it possible to drag blocks into the center panel that controls thebehavior of the button.

Two scripts in the center panel

Although you can't read the details in Image 1 , you can see that there are two scripts showing in the center panel. (I will show you a full-size screen shot of the center panel later in Image 2 .)

For now, suffice it to say that the top script initializes the values stored in all four variables when theuser clicks the green flag in the upper right of Image 1 . The bottom script in the center panel defines the behavior of the program when the userclicks the button in the Stage area.

Variables with sliders

If you look carefully, you can tell that the top two variables that are displayed in the Stage area look different from the bottom two variables.This is because a slider has been assigned to each of the top two variables (see Image 5 ) . This makes it possible for the user to manually set the values stored in each of these two variables.

How to create a slider

To create a slider for a variable, right click on the display of the variable in the Stage area and select slider in the popup menu that appears.

Once you have caused a slider to appear with the variable display, you can right-click on the variable display again and select set slider min and max in the popup menu to specify the range of the slider. This will cause asimple dialog box to appear into which you can enter the minimum value and the maximum value and then click an OK button. In this program, I have bothsliders set to a minimum value of -10 and a maximum value of +10.

Full-size view of the center panel

Image 2 shows a full-size view of the center panel after having selected the button icon in the area immediately below the Stage in Image 1 .

Image 2. full-size view of the center panel.

Missing image.
Image 2. Full-size view of the center panel.

Initialize the variable values to zero

As I mentioned earlier, the top script in Image 2 sets the value of each of the four variables to zero when the user clicks the green flag. The codein that script should be completely familiar to you by now and no explanation should be necessary.

Define the behavior of the button

The bottom script in Image 2 defines the behavior of the program when the button is clicked. Basically, that code says to set the value of thevariable named Sum to the sum of the contents of the two variables named LeftOperand and RightOperand and to set the value of the variable named Diff to the value of the left operand minus the value of the right operand.

Questions & Answers

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
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?
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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
how to synthesize TiO2 nanoparticles by chemical methods
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Berger describes sociologists as concerned with
Mueller 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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