Variables and data types

A variable is a named storage location that holds a value of a particular type. Choosing the right type keeps data correct and memory efficient.

• Declare before use: `var age : integer;` then assign with `age := 16;` (`:=` is assignment, `=` is comparison).
• Core types: integer (whole numbers), real (decimals), string (text), boolean (True/False), char (one character).
• Match the type to the data: a price is real, a quantity is integer, a name is string, a "paid?" flag is boolean.
• Constants (`const VAT = 0.15;`) name fixed values so the code reads clearly and changes in one place.

• Variable — a named, changeable storage location of a given type.
• Data type — the kind of value a variable holds and the operations allowed on it.
• Assignment — giving a variable a value with `:=`.