Renamed createData() to assembleInstruction(); added assembleOperand() method.
Operand assembly and symbol mapping tested successfully.
Updated all tests to reflect use of symbolic memory addressing; instruction assembly tested successfully.
assembleCode() tested successfully with a load instruction.
Trimmed up surplus, old code and comments; re-done load instruction, where source and destination operands were the wrong way round.
Adjusted tests to account for load instruction operands being the wrong way round. Retested successfully.
Re-ordered load instruction operands.