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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

  • Image 1 . Reduced screen shot of program Relational01 in operation.
  • Image 2 . The center programming panel for Relational01.
  • Image 3 . Starting to use an if-else block.
  • Image 4 . Green blocks exposed by clicking the Operators button.
  • Image 5 . Intermediate stage in construction of if-else script.
  • Image 6 . Screen shot of the output from the program named Relational01.
  • Image 7 . Screen shot of the output from the program named Relational02.

General background information

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.

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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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