VDU	19	S 5	Change the colour palette. VDU 19 allows
			any of the 16 available colours to be assigned
			to the colour numbers available in a
			particular mode. In mode 0 (128) for example:
			VDU 19,1,2,0,0,0 changes colour 1
			(normally White) to Green.
			VDU 19,0,7,0,0,0 changes colour 0
			(normally Black) to White.
			The three items at the end of this sequence
			should always be 0.
VDU	20	T 0	Restore default colours (i.e. revert to white
			text / graphics on a black background) and
			reset the palette to its default colour
			assignments.
VDU	21	U 0	Disable the VDU driver (i.e. stop subsequent
			output to the screen).
			Note that [CTRL]+ U issued from the keyboard
			has the effect of deleting the current line.
VDU	22	V 1	Select screen mode. This sequence should not
			be used from the keyboard in languages such
			as BASIC or from the command screens of the
			View family. See the Reference Manual for
			further information.
VDU	23	W 9	Miscellaneous functions.
			VDU 23 provides a great many functions,
			most of which are beyond the scope of this
			guide. The functions are listed below -- details
			of the remaining parameters are given in the
			Reference Manual-
			VDU 23,0 control 6845 directly
			VDU 23,1 change cursor
			VDU 23,2
			VDU 23,3 set full pattern-fill
			VDU 23,4 patterns
			VDU 23,5
			VDU 23,6 set dotted line pattern
			VDU 23,7 scroll window directly
			VDU 23,8 clear block in text window
			VDU 23,9
App 7.3