← IGCSE Computer Science Paper 2

Basic data types in pseudocode

The five basic pseudocode data types: whole numbers, decimals, a single character, text of any length, and TRUE or FALSE. A phone number should be a STRING.

Part of: IGCSE Computer Science 0478 — 7c Pseudocode and Flowcharts — Module 6

Understanding Basic data types in pseudocode in IGCSE Computer Science Paper 2

What it does: Phone numbers are identifiers, not quantities. STRING keeps the leading 0 and any + or spaces. REAL stores numbers with a fractional part. INTEGER would lose the pence. CHAR holds exactly one character. It is written in single quotes in pseudocode. BOOLEAN has only two values: TRUE and FALSE. Do not store them as text. This is the mistake because a CHAR variable cannot store text longer than one character. STRING is the type for text of any length.

Common mistakes: Age is an INTEGER, so it can only hold whole numbers. 15.5 has a fractional part. Use a whole number such as 15, or declare Age as REAL. Price is a REAL, so it needs a number. Quotes make "4.99" a STRING. It should be Price ← 4.99.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 136–145) and word search (Modules 123–145).

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Learning

Duo

Which data type should store the number of students in a class, such as 28?

INTEGERREAL

Matches

DECLARE Grade : CHAR Grade ← "Merit"

↓

CHAR holds only one character, but "Merit" is several characters. Grade should be declared as STRING, or the value should be a single character such as "M".

Applying

Meanings

Term

INTEGER, REAL, CHAR, STRING, BOOLEAN

Meaning

The five basic pseudocode data types: whole numbers, decimals, a single character, text of any length, and TRUE or FALSE. A phone number should be a STRING.

Practice

DECLARE Age : INTEGER

Testing

Gaps

DECLARE Age :

Check Answer

Spots

2DECLARE Phone : STRING

3Age ← 15.5

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Quick Questions

1. Which data type should store the number of students in a class, such as 28?

A. INTEGER ✓

B. REAL

INTEGER stores whole numbers. A count of students is always a whole number.

2. Which data type should store a price such as 3.75?

A. INTEGER

B. REAL ✓

REAL stores numbers with a fractional part. INTEGER cannot hold the .75.

3. Which data type should store a single letter grade such as 'B'?

A. CHAR ✓

B. STRING

CHAR holds exactly one character. It is written in single quotes in pseudocode.

4. Which data type should store a name such as "Amira"?

A. STRING ✓

B. CHAR

STRING holds zero or more characters. A name is longer than one character, so CHAR is too small.

5. Which data type should store a value that can only be TRUE or FALSE, such as whether a door is locked?

A. STRING

B. BOOLEAN ✓

BOOLEAN has only two values: TRUE and FALSE. Do not store them as text.

Match the Pairs

DECLARE Age : INTEGER → Age can only store whole numbers, such as 15 or 42

DECLARE IsPassed : BOOLEAN → IsPassed can only store TRUE or FALSE

A phone number should be stored as text because it can start with 0 and is never used in calculations → DECLARE PhoneNumber : STRING

A price such as 4.99 has a fractional part, so it needs the type for decimal numbers → DECLARE Price : REAL

DECLARE Grade : CHAR Grade ← "Merit" → CHAR holds only one character, but "Merit" is several characters. Grade should be declared as STRING, or the value should be a single character such as "M".

DECLARE Score : INTEGER Score ← 72.5 → INTEGER cannot store a number with a fractional part like 72.5. Score should be declared as REAL, or the value should be a whole number.

Key Term

INTEGER, REAL, CHAR, STRING, BOOLEAN

The five basic pseudocode data types: whole numbers, decimals, a single character, text of any length, and TRUE or FALSE. A phone number should be a STRING.

Fill in the Blanks

1. DECLARE Age : INTEGER Age ← 15

Hint: Type the data type used for whole numbers with no fractional part.

2. DECLARE Price : REAL Price ← 2.75

Hint: Type the data type used for numbers that can have a fractional part.

3. DECLARE Grade : CHAR Grade ← 'A'

Hint: Type the data type that stores exactly one character.

4. DECLARE PhoneNumber : STRING PhoneNumber ← "0123456789"

Hint: Type the data type for text of any length. It suits a phone number because of the leading zero and because you never do sums with it.

5. DECLARE IsValid : BOOLEAN IsValid ← TRUE

Hint: Type the data type that can only hold TRUE or FALSE.

Spot the Error

Question 1

A DECLARE Age : INTEGER

B DECLARE Phone : STRING

C Age ← 15.5

Line C — Age is an INTEGER, so it can only hold whole numbers. 15.5 has a fractional part. Use a whole number such as 15, or declare Age as REAL.

Question 2

A DECLARE Price : REAL

B Price ← "4.99"

C OUTPUT Price

Line B — Price is a REAL, so it needs a number. Quotes make "4.99" a STRING. It should be Price ← 4.99.

Question 3

A DECLARE Grade : CHAR

B INPUT Grade

C Grade ← 'AB'

Line C — A CHAR holds exactly one character. 'AB' is two characters. Use one character such as 'A', or declare Grade as STRING.

Question 4

A DECLARE Phone : INTEGER

B Phone ← "07700900123"

C OUTPUT Phone

Line A — A phone number is not used for arithmetic and often starts with 0, which an INTEGER would lose. It should be declared as STRING.

Question 5

A DECLARE IsOpen : BOOLEAN

B DECLARE Count : INTEGER

C IsOpen ← "TRUE"

Line C — A BOOLEAN holds the values TRUE or FALSE without quotes. "TRUE" in quotes is a STRING. It should be IsOpen ← TRUE.

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