<< Chapter < Page Chapter >> Page >

In addition, I used the pull-down list on each of six blocks to select the name of the variable to which each block applies. (Note that each of those six blocks refers either to Counter or counter .)

Image 5. the finished program.

Missing image.
Image 5. The finished program.

Behavior of the program

Click the green flag

The program contains three scripts. Each script remains silent until a specific event occurs. As the label on the uppermostblock in the top programming script in Image 5 indicates, the code in the top script in Image 5 is executed once each time the user clicks the green flag shown in the upper right of Image 1 . This code causes the values stored in each of the two variables to be set to zero. This, in turn causes thevariable displays in the Stage area to each show a value of 0.

Press the space bar

Because of the top block in the middle script reads "when space key pressed" , the code in the middle script is executed once each time the user presses the space bar.

The pull-down list on this block allows you to select among the keys on the keyboard with the space bar being the default.

One of the orange programming blocks in the middle script causes the value of the variable named Counter to change by +1 when the space bar is pressed. The other orangeprogramming block causes the value of the variable named counter to change by +5 when the space bar is pressed.

In other words, repetitively pressing the space bar causes the Counter variable to count up in increments of one and causes the counter variable to count up in increments of five.

Click the mouse on the Stage

Because of the top block in the bottom script reads "when stage clicked" , the code in the bottom script in Image 5 is executed once each time the user clicks the mouse in the large white Stagearea shown in Image 1 .

The bottom two blocks in this script are the same as the bottom two blocks in the middle script except that the algebraic signs on the two literal values are minus instead of plus.

The absence of a "-" character causes a literal value to be positive. A "+" character is notrequired for positive literal values.

Repetitively clicking the mouse in the Stage area causes the Counter variable to count down in increments of oneand causes the counter variable to count down in increments of five.

Event-driven programming

The ability to write programs that cause certain operations to occur in response to events (such as pressing the space bar and clicking the mouse on the Stage) is often referred to as event-driven programming.

It is easy to write event-driven programs in Scratch. On the other hand, writing event-driven programs is not easy in languages such asJava, C#, and C++. You need quite a lot of programming knowledge to write event-driven programs in those languages.

It is useful to give programming students a taste of event-driven programming early, if for no other reason than the factthat it tends to make programming more interesting.

Example blocks with pointed ends

The blocks shown in Image 6 are not used in this program. They are shown in this module to illustrate blocks with pointed endsreferred to earlier .

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
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
what is the stm
Brian Reply
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?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
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
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 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
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