ADDENDUM to Section 2 -- Updated references for OS 1.2.

LocationLocationComments
OS ?0.1OS 1.2
&320/&321&34EScreen memory start. High byte only in OS 1.2.
&322/&323&350/&351Address of top left of screen.
&324/&325&352/&353Bytes per line.
&326/&327&354Screen memory length. High byte only in OS 1.2.
&328&30BTop right y-coordinate of text window.
&329&30ATop right x-coordinate of text window.
&32A&309Bottom left y-coordinate of text window.
&32B&308Bottom left x-coordinate of text window.
&32C&318Cursor X-coordinate.
&32D&319Cursor Y-coordinate.
&330/&331&306/&307Top right Y-coordinate of graphics window.
&332/&333&304/&305Top right X-coordinate of graphics window.
&334/&335&302/&303Bottom right Y-coordinate of graphics window.
&336/&337&300/&301Bottom right X-coordinate of graphics window.
&338/&339&30E/&30FY-coordinate of graphics origin.
&33A/&33B&30C/&30DX-coordinate of graphics origin.
&33C/&33D&312/&313Current Y-coordinate of graphics cursor.
&33E/&33F&310/&311Current X-coordinate of graphics cursor.
&367&355Current screen mode.
&36B&D0Flags one. [VDU status byte.]
&36D&358CLS/scroll filler byte (actually text background in OS1.2)
&36E&359Graphics foreground colour mask.
&36F&35AGraphics background colour mask.
&370&35BGraphics foreground modifier.
&371&36CGraphics background modifier.
&375&360Colours available.
&376&34FBytes per character.
&377&361Pixels per byte.
&37E&366**Seems to be no equivalent in OS1.2 but location &366 always contains 127.
&382&367Define [font] flags.
-- &368RAM location of characters 224--255,
if bit 1 of &367 is set.
-- &369RAM location of characters 192--223,
if bit 2 of &367 is set.
-- &36ARAM location of characters 160 --191,
if bit 3 of &367 is set.
-- &36BRAM location of characters 128--159,
if bit 4 of &367 is set.
-- &36CRAM location of characters 96--127,
if bit 5 of &367 is set.
-- &36DRAM location of characters 64-- 95,
if bit 6 of &367 is set.
-- &36ERAM location of characters 32--63,
if bit 7 of &367 is set.
&D8&25ACaps lock/shift lock
&38A-&399&36F-&37ECurrent palette.
&CD/&CE&D2/&D3Foreground/background colour masks.

Christopher Dewhurst,
Chelmsford, 2005.