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
Scratch 2.0
(released May 9, 2013) is the second major version of Scratch to be released during the life of theproduct. Among other things, it features a redesigned editor and website, and
allows you to edit projects directly from your web browser.
This module
(tutorial) 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
using
Scratch 2.0 . Information is provided
not only for the beginners themselves but also for their parents and teacherswhere appropriate.
The purpose of this module is to teach you how to write a Scratch program that uses the relational operators
shown below:
<(less than)
= (equal to)>(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 . Project Relational01 at startup.
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Image 2 . Project Relational01 output.
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Image 3 . Reduced screen shot of program
Relational01 programming interface.
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Image 4 . Full size view of the programming panel for Relational01.
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Image 5 . Starting to use an
if-else block.
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Image 6 . Green blocks exposed
by clicking the Operators button.
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Image 7 . Intermediate stage in
construction of if-else script.
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Image 8 . Screen shot of the output from the program named Relational01.
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Image 9 . 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 that 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.
