Variables in Programming - JSS 2 Note

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VARIABLES IN PROGRAMMING

Subject: Digital Technologies
Class: JSS 2
Term: Second Term
Week: 4
Topic: Variables in Programming
Duration: 80 Minutes (Double Period)

1. Learning Objectives

By the end of the lesson, students should be able to:

• Explain the meaning of a variable in programming.
• State the uses of variables in computer programs.
• Identify examples of data that can be stored in variables.
• Create and name variables correctly in Scratch.
• Use variable blocks to store and change values in a simple program.

2. Introduction

In everyday life, we keep records of information such as examination scores, the number of students in a class, money saved, and the number of items sold. These values may change from time to time.

Computer programs also need to store information and change it when necessary. For example, a game may keep track of a player's score, while a quiz program may count the number of correct answers. Variables help programs perform these tasks.

3. Meaning of a Variable

Definition: A variable is a named storage location used by a computer program to hold data or a value that can change while the program is running.

A variable has a name that allows the programmer to identify the information stored in it. The value stored in a variable can be set, displayed, or changed as the program executes.

For example, a game can use a variable called Score to store the player's points. When the player earns more points, the value of Score increases.

Examples of Variables

Variable Name	Possible Value	Purpose
Score	10	Stores a player's score in a game.
StudentName	Amaka	Stores a student's name.
Age	12	Stores a person's age.
Count	5	Keeps track of how many times an action occurs.
Lives	3	Stores the number of lives remaining in a game.

4. Uses of Variables in Programming

Variables are useful in many types of computer programs. Their major uses include:

1. Storing information: Variables hold values such as names, scores, numbers, and counts.
2. Keeping scores: A game can use a Score variable to record points earned by a player.
3. Counting events: A program can count how many times a button is clicked or an action is performed.
4. Updating information: A variable can be changed when a new value is received or an event occurs.
5. Performing calculations: Programs can use variables to store numbers and results of calculations.
6. Making decisions: A program can compare a variable's value with another value to decide what should happen next.

Example: In a quiz game, a Score variable may start at 0. Whenever a student answers a question correctly, the program increases Score by 1.

5. Creating Variables in Scratch

Scratch is a block-based programming environment. It allows users to create variables and control them using programming blocks.

Steps for Creating a Variable

1. Open the Scratch programming environment.
2. Open or select the project you want to work on.
3. Locate the Variables category in the block palette.
4. Click Make a Variable.
5. Type a meaningful name, such as Score.
6. Choose whether the variable should be available to all sprites or only the selected sprite, depending on the project.
7. Click OK.

Scratch creates the variable and provides blocks for setting its value, changing its value, and controlling whether it is displayed on the Stage.

6. Important Variable Blocks in Scratch

Block	Function	Example Use
set [Score] to (0)	Assigns a specific value to a variable.	Sets the score to zero at the beginning of a game.
change [Score] by (1)	Increases or decreases the current value by the specified amount.	Adds one point when a player answers correctly.
show variable [Score]	Displays the variable's value on the Stage.	Allows the player to see the current score.
hide variable [Score]	Hides the variable display from the Stage.	Hides the score when it is not needed on the screen.

Important: The set block replaces the variable's current value with a specified value. The change block adds to or subtracts from its current value.

7. Naming Variables Correctly

A good variable name should describe the information it stores. Meaningful names make programs easier to understand and maintain.

Guidelines for Naming Variables

• Use names that describe the stored information, such as Score, Age, or TotalMarks.
• Avoid confusing names that do not explain the purpose of the variable.
• Keep names reasonably short and meaningful.
• Use a consistent naming style throughout a project.
• Avoid unnecessary spaces and punctuation in variable names, especially when using programming languages with stricter naming rules.

Good Variable Name	What It Stores
StudentName	A student's name.
TotalScore	The total score obtained.
NumberOfItems	The number of items counted.
Lives	The number of lives remaining.

8. Practical Activity: Creating a Score Counter

In this activity, students will create a simple Scratch program that stores and increases a player's score.

Procedure

1. Create a new Scratch project.
2. Create a variable named Score.
3. Add an event block such as when green flag clicked.
4. Attach a set Score to 0 block.
5. Add a suitable event, such as when this sprite clicked.
6. Attach a change Score by 1 block to the sprite-click event.
7. Ensure the Score variable is visible on the Stage.
8. Click the green flag to start the program, then click the sprite several times.
9. Observe how the score changes each time the sprite is clicked.

Illustration of the Program

WHEN GREEN FLAG CLICKED SET Score TO 0 WHEN THIS SPRITE CLICKED CHANGE Score BY 1

The illustration above shows the logic of the program. In Scratch, students should build it by joining the appropriate event and variable blocks.

Expected Result

• At the beginning, Score displays 0.
• After one sprite click, Score becomes 1.
• After five sprite clicks, Score becomes 5.
• The score returns to 0 whenever the green flag is clicked and the reset script runs.

9. Advantages of Using Variables

• They allow programs to store and update information.
• They make it easier to perform calculations.
• They help programs keep scores and counts.
• They support decision-making in programs.
• They make programs more flexible and interactive.

10. Summary

A variable is a named storage location that holds data used by a program. Variables can store information such as scores, names, ages, and counts. Their values can change while a program is running.

In Scratch, variables are created from the Variables category. Important blocks include set, change, show variable, and hide variable. Meaningful variable names help programmers understand their programs. A score counter is a simple example of how variables are used in games and other interactive applications.

11. Evaluation Questions

1. What is a variable in programming?
2. State four uses of variables.
3. Give three examples of variable names and explain what each stores.
4. Describe the steps involved in creating a variable in Scratch.
5. Differentiate between the set and change variable blocks.
6. What is the purpose of the show variable block?
7. Write the steps for creating a simple score counter in Scratch.

12. Assignment

1. Define a variable in your own words.
2. List five examples of information that can be stored in variables.
3. Explain three guidelines for choosing good variable names.
4. Draw or describe a Scratch program that sets a variable named Count to 0 and increases it by 1 whenever a sprite is clicked.
5. State two advantages of using variables in a computer program.

13. Interactive Quiz

Choose the correct answer for each question and click Submit Quiz to check your score.

1. What is a variable in programming?

A physical part of a computer A named storage location for data A type of printer A computer virus

2. Which variable could be used to store a player's points?

Score Keyboard Monitor Speaker

3. Where do you create a variable in Scratch?

Sound category Motion category Variables category Looks category only

4. What does “set Score to 0” do?

Adds 0 to the score without replacing it Replaces the current score with 0 Deletes the Scratch project Increases the score by 1

5. What does “change Score by 1” do?

Hides the score Sets the score to 0 Increases the current score by 1 Creates a new sprite

6. Which is the most meaningful name for a variable storing examination marks?

Thing TotalMarks Abc123xyz ComputerScreen

7. Which block can display a variable's value on the Stage?

Show variable Delete sprite Play sound Move 10 steps

8. If Score is 4 and the program changes it by 1, what is the new value?

0 3 4 5

9. Which of these is a use of variables?

Keeping track of a game score Cleaning a computer screen physically Connecting a power cable by itself Printing without a printer

10. If Score starts at 0 and a player clicks a sprite five times, increasing Score by 1 each time, what is the final score?

1 4 5 10

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