1.5 Scr0350: relational operators in scratch 2.0  (Page 5/6)

• Click the Data button to expose the variables as shown in Image 3 .
• Drag the block for the variable named LeftOperand and drop it in the white box immediately to the left of the left angle bracket operator in Image 7 .
• Drag the block for the variable named RightOperand and drop it in the white box immediately to the right of the left angle bracket operator in Image 7 .

Once we do that, we will have finished the construction of the second script from the top in Image 4 .

Completing the program

Following that, we need to go through essentially the same process to construct the bottom two scripts in Image 4 , using the other two relational operators in Image 6 along with the variables named LeftOperand and RightOperand .

A screen shot of the program output

Image 8 shows a screen shot of the Stage for a given set of values for the variablesnamed LeftOperand and RightOperand .

Figure

Image 8. screen shot of the output from the program named relational01.

Interpretation of the results

The text showing in the bottom three variables tells us that for these values, the relationships among the values are as follows:

The value of the left operand (-4) is less than the value of the right operand (2).

The value of the left operand (-4) is not equal to the value of the right operand (2).

The value of the left operand (-4) is not greater than the value of the right operand (2).

If you move the sliders to change the values in the left and right operand variables and then click the button, you are likely to get different results.

An online version of this program is available

A copy of this program has been 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 .

Run the program

I encourage you to use the information provided above to write this program. Experiment with the code, making changes, and observing the results of yourchanges. Make certain that you can explain why your changes behave as they do.

Just for fun, see if you cause a short drum roll to be produced by your computer speakers each time the button is clicked.

I also encourage you to write the program described below.

Student programming project

Write a project named Relational02 that meets the following specifications:

This program illustrates the use of the following relational operators in addition to arithmetic operators:

This is an upgrade to the program named Relational01 .

The program creates the following six variables and a button and displays them on the stage as shown in Image 9 :

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

Figure

Image 9. screen shot of the output from the program named relational02.

Operation of the program

When the user clicks the green flag, the values of all six variables shown in Image 9 are set to 0.

The user slides the three sliders to set the values of LeftOperand , RightOperand , and Offset .