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In this module, I will present and explain a Scratch program named Logical01 . This program illustrates the use of the and , or , and not operators in Scratch. These are called logical operators.

In this module, I will provide an explanation of logical operators and truth tables . Then I will present and explain a Scratch program that illustrates the use of the logical and , or , and not operators when used in conjunction with relational operators. You learned about relational operators in an earlier module.

Finally, I will provide the specifications for two programming projects for you to demonstrate your understanding of what you learned from the first programand from earlier modules. One of the programming projects is relatively difficult requiring an understanding of DeMorgan's theorem .

Copies of all three programs will be posted online for your review (see Resources for the URL) . If you don't find the program using that URL, search the Scratch site for the usernamed dbal .

A real-world example

Logical operators can be confusing at first glance, but perhaps a real world example will help to eliminate some of that confusion. For many years in thiscountry, we have had a movie rating system designed to control the viewing of objectionable content by young people. According to Wikipedia , the R rating means something like the following:

"Restricted - Under 17 requires accompanying parent or adult 17 or older with photo ID"

Formulate this using logical operator concepts

In most cases, this means that a person will be allowed entry into the theatre to view the movie if:

  • The person has the price of admission and is older than 16, or
  • The person has the price of admission and is under 17 and is accompanied by an adult who also has the price of admission and the adult can show a photo ID.

Note the use of the boldface Italicized words or and and in the above example.

The not operator

The not operator is a little more difficult to explain in terms of real world examples. At this point, suffice it to say that the application ofthe not operator causes something that is true to become false and causes something that is false to become true. For example, if someone is older than16, that person is not 16 or younger.

The reality - logic in a formal sense

The reality is that you have been dealing with this kind of logic most of your life. However, unless you had a specific reason to do so, such as being acomputer programmer, a computer engineer, or perhaps an attorney, you may never have thought about it in a formal sense. The time to think about it in a formalsense has arrived.

A sample program named Logical01

A button and s even variables

This program creates a button along with the following seven variables.

A (a slider variable) B (a slider variable)C (a slider variable) D (a slider variable)A<B and C<D not(A<B and C<D) A<B or C<D

The program displays the button and the variables on the Stage and initializes all of the variables to zero when the user clicks the green flag asshown in Image A .

Image a. reduced screen shot of the programmer interface for the program named logical01.

Missing image
Image A. Reduced screen shot of the programmer interface for the program named Logical01.

Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
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Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
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what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
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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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