1.2 Scr0320: memory, variables, and literals in scratch 2.0  (Page 7/11)

• Identify the variable to which that block applies by selecting the variable name in the pull-down list built into the block.
• Enter a literal numeric or string value from the keyboard into the white or gray text field at the right end ofthe block, or
• Drag some other block and drop it into the white or gray text field.

There are at least two different shapes that are eligible for being dropped into such text fields:

1. A horizontal rectangle with rounded corners such as the orange block labeled Counter in Image 1 . (This shape seems to always be associated with a numeric or string value.)
2. A horizontal rectangle with pointed ends as shown by several of the blocks in Image 4 . (This shape seems to always be associated with a boolean result of true or false.)

Blocks having the rounded corners are eligible for being dropped into the white text fields with rounded corners of the programming blocks in Image 1 .

Blocks having the pointed ends are eligible for being dropped into the darker orange text fields having a similar shape on the blocks that areexposed by clicking the Control button in the programming interface.

Either shape of block is eligible for being dropped into the white text fields withsquare corners shown in Image 1 . Thus the block in Image 1 that is used to set a variable to a value can set the value to a numeric value,a string value, or a boolean value.

(Note that the two variable blocks shown in Image 1 labeled Counter and counter are eligible for being dropped into the white text fields ofthe two programming blocks shown in Image 1 . This makes it possible to cause the value of one variable to depend on the valueof another variable.)

If you click the Operators button shown in Image 1 (see Image 4 ) you will expose several different blocks with rounded corners that are eligible for being dropped into thewhite text fields in Image 1 according to the rules described above.

Cause the variables to be displayed

As mentioned earlier, checking the boxes to the left of the variable names in Image 1 causes them to be displayed in the upper-left corner of the Stage shown in Image 1 . (Clicking the show and hide blocks will also check and uncheck the checkboxes, which in turn will show or hide the variables on the stage.)

Create a new variable

You create a new variable by clicking the button labeled Make a variable shown in Image 1 . When you click that button, the dialogshown in Image 2 appears on the screen asking you to provide the name for the new variable.

Figure

Image 2. dialog for entering a variable name.

At that point, you simply type in the name for the new variable and click the OK button.

The radio buttons on that dialog allow you to specify which sprites have access to the variable.

The disabled cloud variable button (shown in light gray in Image 2 ) is a new feature of Scratch 2.0. Apparently registered users who are signed in can check that button and save the variable on the MITwebsite or on a website controlled by MIT. I wasn't signed in, which is why it was disabled.