The following syntax diagrams show the syntax of: • a variable • an unsigned integer • a letter a digit • an operator • an assignment statement. [Figure X.X showing syntax diagrams for variable, unsigned integer, letter, digit, operator, assignment statement]

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

1. [2] • An unsigned integer,12, is used instead of the last variable // 12 is not a valid variable • The variable Z is not a valid variable / missing an unsigned integer after the 2
2. [5] One mark per bullet point • <variable> ::= <letter><unsigned_integer> • <unsigned_integer> ::= <digit>|<digit><digit> • <digit> ::= 1 | 2 | 3 and <operator> ::= + | - | * • <assignment_statement> ::= <variable>= <variable><operator><variable>
3. [3] One mark adding both boxes... unsigned integer unsigned integer One mark for correct position(s) and connector(s) ... One mark ... rest correct (assignment statement) [Diagram showing a variable pointing to an equal sign, then branching to either a variable or unsigned_integer, then an operator, then another branch to either a variable or unsigned_integer]
4. [3] Max three One mark for <assignment_statement>::=<variable>= One mark two or three correct options or two marks if all four options correct <variable><operator><variable> |<variable><operator><unsigned_integer> |<unsigned_integer><operator><variable> |<unsigned_integer><operator><unsigned_integer> or One mark for each section <operand>::=<variable>|<unsigned integer> <assignment_statement>::=<variable>= <operand><operator><operand>