← IGCSE Computer Science Paper 2

Identifier rules in Cambridge pseudocode

The name of a variable, constant, procedure or function. Use PascalCase: letters and digits only, no spaces or underscores, start with a capital letter, e.g. FirstName.

Part of: IGCSE Computer Science 0478 — 8.1a Data Types and Variables — Module 3

Understanding Identifier rules in Cambridge pseudocode in IGCSE Computer Science Paper 2

What it does: TotalScore joins two words with no space or underscore, and each word starts with a capital letter, which is the PascalCase style. FirstName uses PascalCase with letters only. Underscores are not allowed in identifiers. Keywords such as OUTPUT, IF and INPUT are reserved for the language, so they cannot be used as identifiers. An identifier is the name given to a variable, constant, procedure or function.

Common mistakes: An identifier cannot contain spaces, so 'First Name' is read as two separate words. It should be INPUT FirstName. Identifiers may only use letters and digits, so underscores are not allowed. Use PascalCase: DECLARE TotalScore : INTEGER.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 307–316) and word search (Modules 296–316).

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Learning

Duo

Which identifier follows the Cambridge pseudocode rules?

FirstNamefirst_name

Matches

DECLARE first_name : STRING

↓

The identifier contains an underscore. Only letters and digits are allowed, so it should be FirstName.

Applying

Meanings

Term

identifier

Meaning

The name of a variable, constant, procedure or function. Use PascalCase: letters and digits only, no spaces or underscores, start with a capital letter, e.g. FirstName.

Practice

DECLARE FirstName : STRING

Testing

Gaps

OUTPUT

Check Answer

Spots

2DECLARE Age : INTEGER

3INPUT First Name

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Quick Questions

1. Which identifier follows the Cambridge pseudocode rules?

A. first_name

B. FirstName ✓

FirstName uses PascalCase with letters only. Underscores are not allowed in identifiers.

2. Which identifier is valid?

A. TotalScore ✓

B. Total Score

Identifiers cannot contain spaces. Join the words together in PascalCase: TotalScore.

3. Which identifier is valid?

A. 1Player

B. Player1 ✓

An identifier cannot start with a digit. Digits are allowed, but only after the first letter, as in Player1.

4. Which identifier is valid?

A. Price ✓

B. Price$

Identifiers can only contain letters and digits. Symbols such as $ are not allowed.

5. Which identifier is valid?

A. Cafe ✓

B. Café

Accented letters like é are not allowed. Use only the plain letters A-Z and a-z.

Match the Pairs

FirstName → A valid identifier: PascalCase, letters only, starts with a capital letter

Score2 → A valid identifier that uses a digit after the first character

An identifier must not contain spaces or underscores, so join the words together in PascalCase → DECLARE TotalScore : INTEGER

An identifier can be the name of a constant as well as a variable, and it still follows the PascalCase rules → CONSTANT PassMark ← 50

DECLARE first_name : STRING → The identifier contains an underscore. Only letters and digits are allowed, so it should be FirstName.

DECLARE 2ndScore : INTEGER → The identifier starts with a digit. An identifier must start with a capital letter, so it should be SecondScore.

Key Term

identifier

The name of a variable, constant, procedure or function. Use PascalCase: letters and digits only, no spaces or underscores, start with a capital letter, e.g. FirstName.

Fill in the Blanks

1. DECLARE FirstName : STRING FirstName ← "Ava" OUTPUT FirstName

Hint: Type the PascalCase identifier of the variable declared on the first line.

2. DECLARE TotalScore : INTEGER TotalScore ← 0 OUTPUT TotalScore

Hint: Type the keyword that creates a variable. A keyword like this is reserved, so it can't be used as an identifier.

3. DECLARE Score2 : INTEGER Score2 ← 10 OUTPUT Score2

Hint: Type the identifier from the first line. It has a digit after the letters, which is allowed.

4. CONSTANT MaxScore ← 100 OUTPUT "Top mark:" OUTPUT MaxScore

Hint: Type the identifier of the constant. Each new word in it starts with a capital letter, with no spaces or underscores.

5. DECLARE TotalCost : REAL TotalCost ← 9.5 OUTPUT TotalCost

Hint: Type the reserved keyword that displays a value. Keywords like this can't be used as identifiers.

Spot the Error

Question 1

A DECLARE FirstName : STRING

B DECLARE Age : INTEGER

C INPUT First Name

D OUTPUT FirstName

Line C — An identifier cannot contain spaces, so 'First Name' is read as two separate words. It should be INPUT FirstName.

Question 2

A DECLARE Score : INTEGER

B DECLARE Total_Score : INTEGER

C TotalScore ← Score * 2

Line B — Identifiers may only use letters and digits, so underscores are not allowed. Use PascalCase: DECLARE TotalScore : INTEGER.

Question 3

A DECLARE 1stPlayer : STRING

B INPUT FirstPlayer

C OUTPUT FirstPlayer

Line A — An identifier cannot start with a digit. It must start with a letter, so the line should be DECLARE FirstPlayer : STRING.

Question 4

A DECLARE Price : REAL

B DECLARE Quantity : INTEGER

C INPUT Quantity

D Price ← Quantité * 2.5

Line D — Identifiers cannot contain accented letters such as é. Only the plain letters A-Z and digits are allowed, so it should be Quantity.

Question 5

A CONSTANT MaxMark ← 100

B DECLARE Mark : INTEGER

C INPUT Mark$

D OUTPUT Mark, MaxMark

Line C — Symbols such as $ cannot be used in identifiers. Only letters and digits are allowed, so it should be INPUT Mark.

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