The purpose of this module is to teach you how to write a Scratch program that uses the following relational operators: less than, equal to, and greater than.
Table of contents
Preface
This module is one in a collection of modules designed to help beginners
of all ages
(8 and up) learn how to create the code for computer
programs. Information is provided not only for the beginners themselves butalso for their parents and teachers where appropriate.
The purpose of this module is to teach you how to write a Scratch program that uses the following relational operators:
less than ,
equal to , and
greater than .
Viewing tip
I recommend that you open another copy of this module in a separate
browser window and use the following links to easily find and view the images while you are reading about them.
Images
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Image 1 . Reduced screen shot of
program Relational01 in operation.
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Image 2 . The center programming
panel for Relational01.
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Image 3 . Starting to use an
if-else block.
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Image 4 . Green blocks exposed
by clicking the Operators button.
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Image 5 . Intermediate stage in
construction of if-else script.
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Image 6 . Screen shot of the
output from the program named Relational01.
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Image 7 . Screen shot of the
output from the program named Relational02.
First, a quick review of material from earlier modules:
-
Operators are the action elements of a computer program. They
perform actions such as adding two variables.
-
Operands are the things that are operated on by operators. For
example, variables are often the operands that are operated on by operators.
- An
expression is a specific combination of operators and
operands, which evaluates to a particular result.
- A
statement is a specific combination of expressions.
- The equal character (=) would commonly be called the
assignment operator in programming languages such as Java but we will see later that it is used as a
relational operator in Scratch.
- Scratch has two types of data
(numeric and string).
- An operator that operates on one operand is called a
unary operator.
- An operator that operates on two operands is called a
binary operator.
- An operator that operates on three operands is called a
ternary operator. Scratch doesn't have any ternary operators.
-
Binary operators in Scratch use
infix notation. This means that the operator appears between its operands.
