← IGCSE Computer Science Paper 2

Data type keywords: INTEGER, REAL, CHAR, STRING, BOOLEAN

The five data types, in order: whole number, number with a fractional part, one character, zero or more characters, TRUE or FALSE. A phone number is a STRING.

Part of: IGCSE Computer Science 0478 — 7a Program Development Life Cycle — Module 24

Understanding Data type keywords: INTEGER, REAL, CHAR, STRING, BOOLEAN in IGCSE Computer Science Paper 2

What it does: Phone numbers and postcodes are identifiers, not quantities, so they are STRING values. An INTEGER would drop a leading 0. REAL holds numbers with a fractional part. INTEGER can only hold whole numbers, so it cannot store 3.75. CHAR holds a single character. A STRING holds zero or more characters, so it is used for longer text. BOOLEAN holds only TRUE or FALSE. It is the right type for yes/no values. A type check confirms the input is the expected data type. A whole number age is an INTEGER, so a value like 14.5 would fail.

Common mistakes: Age is an INTEGER, so it can only hold a whole number. 15.5 has a fractional part. It should be a whole number such as 15, or Age should be declared as REAL. The Cambridge keyword for a single character is CHAR, not CHARACTER. It should be DECLARE Initial : CHAR.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 17–26) and word search (Modules 1–26).

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Learning

Duo

Which data type should a variable holding a student's age in whole years use?

STRINGINTEGER

Matches

DECLARE Postcode : INTEGER

↓

A postcode can start with 0 or contain letters, and you never do sums with it. It should be a STRING, not an INTEGER.

Applying

Meanings

Term

INTEGER, REAL, CHAR, STRING, BOOLEAN

Meaning

The five data types, in order: whole number, number with a fractional part, one character, zero or more characters, TRUE or FALSE. A phone number is a STRING.

Practice

DECLARE Age : INTEGER

Testing

Gaps

DECLARE Age :

Check Answer

Spots

3Price ← 2.50

4Age ← 15.5

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Quick Questions

1. Which data type should a variable holding a student's age in whole years use?

A. STRING

B. INTEGER ✓

A whole number with no fractional part is an INTEGER. You can do arithmetic with it, such as working out next year's age.

2. Which data type suits a price such as 4.75?

A. REAL ✓

B. INTEGER

REAL holds numbers with a fractional part. An INTEGER cannot store the .75.

3. Which data type is best for a phone number such as 07911123456?

A. INTEGER

B. STRING ✓

A phone number is a STRING. You never do arithmetic on it, and an INTEGER would drop the leading 0.

4. Which data type holds exactly one letter, such as a grade 'B'?

A. CHAR ✓

B. STRING

CHAR holds a single character. A STRING holds zero or more characters, so it is used for longer text.

5. Which data type suits a postcode such as SW1A 2AA?

A. STRING ✓

B. CHAR

A postcode has several characters, including letters, digits and a space, so it is a STRING. A CHAR holds only one character.

Match the Pairs

DECLARE Age : INTEGER → Age can hold only whole numbers, such as 15 or 42, with no fractional part.

DECLARE Grade : CHAR → Grade holds exactly one character, such as 'A'.

A phone number or postcode must be stored as a STRING, because it can start with 0 and is never used in sums. → DECLARE PhoneNumber : STRING

A price such as 3.75 has a fractional part, so it needs the REAL data type, not INTEGER. → DECLARE Price : REAL

DECLARE Postcode : INTEGER → A postcode can start with 0 or contain letters, and you never do sums with it. It should be a STRING, not an INTEGER.

DECLARE IsLoggedIn : STRING → A value that is only TRUE or FALSE should use the BOOLEAN data type, not STRING.

Key Term

INTEGER, REAL, CHAR, STRING, BOOLEAN

The five data types, in order: whole number, number with a fractional part, one character, zero or more characters, TRUE or FALSE. A phone number is a STRING.

Fill in the Blanks

1. DECLARE Age : INTEGER

Hint: Type the data type used for a whole number such as an age.

2. DECLARE Price : REAL

Hint: Type the data type for a number that can have a fractional part, like a price.

3. DECLARE Grade : CHAR

Hint: Type the data type that holds exactly one character, like a letter grade.

4. DECLARE PhoneNumber : STRING

Hint: Type the data type for text, which also suits phone numbers because they can start with a zero.

5. DECLARE IsValid : BOOLEAN

Hint: Type the data type for a value that can only be TRUE or FALSE.

Spot the Error

Question 1

A DECLARE Age : INTEGER

B DECLARE Price : REAL

C Price ← 2.50

D Age ← 15.5

Line D — Age is an INTEGER, so it can only hold a whole number. 15.5 has a fractional part. It should be a whole number such as 15, or Age should be declared as REAL.

Question 2

A DECLARE Initial : CHARACTER

B Initial ← 'K'

C OUTPUT Initial

Line A — The Cambridge keyword for a single character is CHAR, not CHARACTER. It should be DECLARE Initial : CHAR.

Question 3

A // Store a phone number

B DECLARE Name : STRING

C INPUT Name

D DECLARE Phone : INTEGER

E INPUT Phone

Line D — A phone number is not used for calculations and often starts with 0, which an INTEGER would drop. It must be a STRING, so: DECLARE Phone : STRING.

Question 4

A DECLARE Passed : BOOLEAN

B Passed ← "TRUE"

C IF Passed = TRUE THEN

D OUTPUT "Well done"

E ENDIF

Line B — A BOOLEAN holds the value TRUE or FALSE, written without quotes. "TRUE" in quotes is a STRING. It should be Passed ← TRUE.

Question 5

A DECLARE Count : INTEGER

B DECLARE Height REAL

C Height ← 1.75

Line B — A declaration needs a colon between the identifier and the data type. It should be DECLARE Height : REAL.

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