What a variable is

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Quick Questions

Shade in the A or B circle for each question.

1. Which statement describes a variable?

A A named storage location whose value can change while the program runs

B A named storage location whose value can never change once set

2. A program sets Score ← 0 and later Score ← 10. What is true about Score?

A It now holds both 0 and 10 at the same time

B Its value changed from 0 to 10, so it is a variable

3. What does the name of a variable, such as Score, do?

A It is the value that is stored in memory

B It labels a place in memory where a value is stored

4. Why do programs use variables?

A To remember values such as a player's score while the program runs

B To make the program run without using any memory

5. Lives ← 3 is followed by Lives ← 2. What is the value of Lives afterwards?

A 2

B 3

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Score ← 0		AScore ← Score + 5
2Score ← 10		BReplaces the old value of Score with 10, showing that a variable's value can change
3A variable is a name that labels a place in memory where a value is kept		CWrong: after Score ← 10 the old value is gone. Score now holds 10, because a variable's value can be replaced.
4A program can change the value held in a variable while it runs		DDECLARE Score : INTEGER
5Score ← 0 Score ← 10 // Score is still 0 now		EStores the value 0 in the variable Score, so the program remembers the starting score
6// A variable's value can never change once it is set Score ← 0		FWrong: a variable's value can change while the program runs. It is a constant whose value cannot change.

Definitions

variable

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Score ← 0 _____ ← 10 OUTPUT Score

Lives _ 3 Lives ← 2 OUTPUT Lives

Score ← 0 Score ← __ OUTPUT Score

Level ← 1 Level ← 2 ______ Level

Lives ← 3 Lives ← 2 OUTPUT _____

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A DECLARE Score : INTEGER

B Score ← 0

C OUTPUT Score

D 10 ← Score

E OUTPUT Score

Question 2

A DECLARE Lives : INTEGER

B Lives ← 3

C Lives = Lives - 1

D OUTPUT Lives

Question 3

A DECLARE Score : INTEGER

B Score 0

C Score ← 10

D OUTPUT Score

Question 4

A DECLARE Age : INTEGER

B Age ← 14

C OUTPUT Age

D Agee ← 15

E OUTPUT Age

Question 5

A DECLARE Name : STRING

B Name ← "Sam"

C Name ← Alex

D OUTPUT Name

Answer Key

What a variable is

Section A: Quick Questions

A — A named storage location whose value can change while the program runs

B — Its value changed from 0 to 10, so it is a variable

B — It labels a place in memory where a value is stored

A — To remember values such as a player's score while the program runs

A — 2

Section B: Match the Pairs

Score ← 0 → Stores the value 0 in the variable Score, so the program remembers the starting score

Score ← 10 → Replaces the old value of Score with 10, showing that a variable's value can change

A variable is a name that labels a place in memory where a value is kept → DECLARE Score : INTEGER

A program can change the value held in a variable while it runs → Score ← Score + 5

Score ← 0 Score ← 10 // Score is still 0 now → Wrong: after Score ← 10 the old value is gone. Score now holds 10, because a variable's value can be replaced.

// A variable's value can never change once it is set Score ← 0 → Wrong: a variable's value can change while the program runs. It is a constant whose value cannot change.

Section C: Definitions

variable — A named storage location in memory whose value can change while a program runs, such as Score going from 0 to 10. Programs use it to remember values.

Section D: Fill in the Blanks

Score ← 0
Score ← 10
OUTPUT Score

Lives ← 3
Lives ← 2
OUTPUT Lives

Score ← 0
Score ← 10
OUTPUT Score

Level ← 1
Level ← 2
OUTPUT Level

Lives ← 3
Lives ← 2
OUTPUT Lives

Section E: Spot the Error

D — The variable name must be on the left of ←, because the value is stored into the variable. A number cannot be a storage location. It should be Score ← 10.

C — A new value is stored in a variable with the assignment arrow ←, not =. It should be Lives ← Lives - 1, which replaces 3 with 2.

B — A value is stored in a variable using the assignment operator ←. Without it, the variable is never given its starting value. It should be Score ← 0.

D — Agee is a different name from Age and was never declared. The value of the variable Age would not change. It should be Age ← 15.

C — Text values must be in double quotes. Without quotes, Alex looks like another variable name. It should be Name ← "Alex".