IGCSE Computer Science Paper 2 Definitions Worksheet: 8.1a Data Types and Variables (Modules 317–326)
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Key terms
Write what each term means, in your own words.
1
TotalToPay ← NumberOfHours * HourlyRate
2
type mismatch
3
CONSTANT HourlyRate ← 6.50
4
CONSTANT Rate ← 6.50
5
CONSTANT VatRate ← 0.2
6
CONSTANT
7
INTEGER
8
REAL
9
CHAR
10
STRING
Answer Key
IGCSE Computer Science Paper 2 · Modules 317–326 · Student wording will vary for definitions
1TotalToPay ← NumberOfHours * HourlyRate — The expression on the right is worked out first, then its result is stored in the variable on the left, replacing any old value that variable held.
2type mismatch — An error when a value assigned to a variable has a different data type from the one it was declared with, such as storing a name in an INTEGER variable.
3CONSTANT HourlyRate ← 6.50 — Declares a named value that is set once. No DECLARE line or data type is needed: the type comes from the literal, so 6.50 makes it REAL. The value cannot change later.
4CONSTANT Rate ← 6.50 — A constant must be set to a literal value, such as 6.50. It cannot be given a variable, another constant or an expression like Rate * 2.
5CONSTANT VatRate ← 0.2 — A named value used instead of a magic number. It makes code easier to read, and when the value changes you edit it in one place only, so no missed edits cause mistakes.
6CONSTANT — Use CONSTANT for a value fixed while the program runs, e.g. VAT rate or pi. Use a variable (DECLARE) for a value that changes or is input, e.g. score or answer.
7INTEGER — The data type for a whole number with no fractional part, written in denary digits, such as 5 or -3. Used for counts like lives: DECLARE Lives : INTEGER
8REAL — The data type for a number that can have a fractional part, written with a digit on each side of the point, such as 4.7 or 0.3. 5 is an INTEGER but 5.0 is REAL.
9CHAR — The data type for exactly one character (a letter, digit or symbol), written in single quotes, such as 'x', '7' or '@'. Even '7' is a character, not a number.
10STRING — The data type for text: zero or more characters written between double quotes, such as "This is a string". "" is the empty string and "123" is text, not a number.