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Operator categories

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

  • arithmetic
  • relational
  • logical
  • bitwise
  • assignment

An earlier module explained arithmetic operators. This module will explain relational operators. Future modules will explain the other kinds of operators.

A previous module introduced you to the selection structure. This module will expand on that concept.

Preview

In this module, I will present and explain a Scratch program named Relational01 . This program illustrates the use of the following relational operators :

<(less than) = (equal to)>(greater than)

The program creates five variables with the names listed below along with a button and displays them on the Stage as shown in Image 1 .

  • LeftOperand - a slider
  • RightOperand - a slider
  • LessThan
  • Equals
  • GreaterThan

Image 1. project relational01 at startup.

Missing image.
Image 1. Project Relational01 at startup.

Image 1 is what you should see on the left side of your screen when you navigate to the project (see Resources ) and click the large green flag. Note the values showing in each of the orange boxes.I will have more to say about them later.

Image 2 shows the result of moving the thumb on the top slider one click to the left (move to -1) and then clicking the button at the bottom. Once again, note the values showing in the orange boxes, which I will have more to say about later.

Image 2. project relational01 output.

Missing image
Image 2. Project Relational01 output.

Image 3 shows a reduced view of the programming interface immediately after having clicked the green flag. Although it is not easy to see, thevariables on the stage match Image 1 .

Image 3. reduced screen shot of program relational01 programming interface.

Missing image
Image 3. Reduced screen shot of program Relational01 programming interface.

Program operation

When the user clicks the green flag, the values of the slider variables shown in Image 1 are set to 0. Expressions containing relational operators are evaluated to set the values of the bottom three variables to theboolean values of true or false.

The user slides the two sliders to change the values of LeftOperand and RightOperand .

When the user clicks the button at the bottom of Image 1 , three separate event handlers on the button test the left operand against the right operand for less than , equal to , and greater than and display string values describing the results in the three variables having the corresponding names in Image 1 and Image 2 . Those three event handlers are shown as the bottom three scripts in the programming panel of Image 3 .

Discussion and sample code

A button and five variables

As you can immediately below the stage in Image 3 , a button was added to this program. If you examine the toolbox and the stage in Image 3 , you will see that five variables were created for the program and that all fiveof the variables were displayed in the Stage. (The checkboxes for all five variables were checked causing them to appear in the Stage.) A better view of the Stage is provided in Image 1 .

Questions & Answers

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Muhammad
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studies of microbes
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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
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they make spores
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food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
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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).
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Give Examples of thermophilic organisms
Shu
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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!
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cell is the smallest unit of life
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Innocent
cell is the structural and functional unit of life
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is the fundamental units of Life
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part of a tissue or an organ being wounded or bruised.
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Binomial nomenclature
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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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