The following instructions cleverly copy the even bits of the supplied byte to the odd bits. In effect making the permanent bits the same as the temporary ones.

		RLCA		Move the mask leftwards.
		XOR	(HL)	Impress onto the mask
		AND	+AA	only the even bits of the
		XOR	(HL)	other byte.
		LD	(HL),A	Restore the result.
		RET

THE 'COMMAND CLASS 09' ROUTINE
This routine is used by PLOT, DRAW & CIRCLE statements in order to specify the default conditions of 'FLASH 8; BRIGHT 8; PAPER 8;' that are set up before any embedded colour items are considered.

1CBE	CLASS-09	CALL	2530,SYNTAX-Z	Jump forward if
		JR	Z,1CD6,CL-09-1	checking syntax.
		RES	0,(TV-FLAG)	Signal 'main screen'.
		CALL	0D4D,TEMPS	Set the temporary colours for
				the main screen.
		LD	HL,+5C90	This is MASK-T.
		LD	A,(HL)	Fetch its present value but
		OR	+F8	keep only its INK part
				'unmasked'.
		LD	(HL),A	Restore the value which now
				indicates 'FLASH 8; BRIGHT 8;
				PAPER 8;'.
		RES	6,(P-FLAG)	Also ensure NOT 'PAPER 9'.
		RST	0018,GET-CHAR	Fetch the present character
				before continuing to deal with
				embedded colour items.
1CD6	CL-09-1	CALL	21E2,CO-TEMP	Deal with the locally dominant
				colour items.
		JR	1C7A,EXPT-2NUM	Now get the first two operands
				for PLOT, DRAW or CIRCLE.

THE 'COMMAND CLASS 0B' ROUTINE
This routine is used by SAVE, LOAD, VERIFY & MERGE statements.

1CDB	CLASS-0B	JP	0605,SAVE-ETC	Jump to the cassette
				handling routine.

THE 'FETCH A NUMBER' SUBROUTINE
This subroutine leads to a following numeric expression being evaluated but zero being used instead if there is no expression.

1CDE	FETCH-NUM	CP	+0D	Jump forward if at the end
		JR	Z,1CE6,USE-ZERO	of a line.
		CP	+3A	But jump to EXPT-1NUM unless
		JR	NZ,1C82,EXPT-1NUM	at the end of a statement.

The calculator is now used to add the value zero to the calculator stack.

1CE6	USE-ZERO	CALL	2530,SYNTAX-Z	Do not perform the operation
		RET	Z	if syntax is being checked.
		RST	0028,FP-CALC	Use the calculator.
		DEFB	+A0,stk-zero	The 'last value' is now zero.
		DEFB	+38,end-calc
		RET		Return with zero added to the
				stack.

THE COMMAND ROUTINES
The section of the 16K monitor program from 1CEE to 23FA contains most of the command routines of the BASIC interpreter.