A variable is a named memory location whose value can change. A constant has a value that does not change while the program runs (e.g. VAT rate).
Assignment stores a value: score = 10. Use meaningful names (e.g. totalCost) and consistent style.
Variables and constants
Data types
Integer (whole numbers), real (numeric values that can include a fractional part; an integer-valued number can also be stored using a real type). Floating-point is a finite representation and may involve rounding, Boolean (True/False), character (a single symbol), string (text).
Casting converts between types: converting the string "12" to integer 12, or 7 to the string "7".
Choosing a data type
Operators
Arithmetic: + - * / MOD (remainder) DIV (integer division) ^ (exponent). Example: 17 MOD 5 = 2; 17 DIV 5 = 3.
Comparison: = (or ==), ≠, <, >, ≤, ≥.
Boolean: AND, OR, NOT.
Operators
Input and output
INPUT reads data (usually a string, then cast); OUTPUT or print displays data.
Order of operations
Brackets first, then exponents, multiplication and division, then addition and subtraction.
Good practice
Declare variables, choose appropriate types, and comment code.
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