80-Bus News

  

May–June 1984, Volume 3, Issue 3











Page 22 of 51











As a brief aside on FILL routines – You can always tell a recursive based FILL routine, as, when it is filling a complex area, there are often pauses while nothing apparently happens on the screen. What is actually happening is that the FILL routine has just filled to a ‘dead end’, and there then follows a period where the recursive structure ‘unwinds’ itself, returning from layer to layer back up the stack until it finds an area that it has not yet filled.

BUG TIME

Well folks, it had to happen. Between writing the first part of this article and completing this one someone has unearthed a bug that is present in both the IVC and SVC monitors. That fact that it has taken so long to surface is indicative that none of you are likely to have met it yet (otherwise you would have reported it – wouldn’t you?). It is in the ESC “f” ... sequence that allows you to redfine the function keys from a program. If you try and ‘undefine’ a key using this sequence the key is not actually fully deleted from the function key table, and if the key is subsequently pressed something will be returned to the host system. What the ‘something’ is cannot be easily predicted. Key definitions can be removed totally from the table, but only by using the Shift/​Edit feature direct from the keyboard.

TABLE 1: Extra features of the SVC

HEXASCIIDECIMALCOMMAND
General
07^G7Bell – sound on-board buzzer
Cursor Movement
1B 0C<ESC> ^L27 12Cursor home
Screen format
1B 34<ESC> “4”27 52Select graphics mode
1B 70...<ESC> “p”...27 112...Select display/​update partition
Character set
1B 67...<ESC> “g”...27 103...Set Language
1B 62...<ESC> “b”...27 98...Read back character set
256x256 graphics
1B 52<ESC> “R”...27 82...Reset point X,Y
1B 53...<ESC> “S”...27 83...Set point X,Y
1B 54...<ESC> “T”...27 84...Test point X,Y
1B 6C...<ESC> “l”...27 108...Draw/​Erase/​Complement a line
1B 6F...<ESC> “o”...27 111...Draw/​Erase/​Complement a circle
1B 6D...<ESC> “m”...27 109...Move cursor to X,Y
1B 77<ESC> “w”...27 119Fill a polygon
1B 64...<ESC> “d”...27 100...Graphics screen dump
Keyboard
1B 3E...<ESC> “>”...27 62...Download soft-key display
Clock
1B 74...<ESC> “t”...27 116...Set clock time
1B 74 3D..<ESC> “t=”...27 116 61.Position clock display
1B 74 45<ESC> “tE”27 116 69Enable clock display
1B 74 44<ESC> “tD”27 116 68Disable clock display
1B 74 3F<ESC> “t?”27 116 63Return clock time
Miscellaneous
1B 61...<ESC> “a”...27 97...Set/reset attributes


This is an OCR’d version of the scanned page and likely contains recognition errors.











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