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.


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 “e” J... sequence that allows you to redfine the function keys from a program. I8 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

HEX ASCIL DECIMAL COMMAND General O7 “6 7 Bell – sound on-board buzzer

Cursor Movement 1B OC <ESC> “L 27 12 Cursor home

Screen format 1B 34 <ESC> “4” 27 52 Select graphics mode 1B 70... <ESC> “p"... 27 112... Select display/update partition


Character set iB G7... CESC> “g"... 27 103... Set Language IB 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> “IT"... 27 84... Test point X,Y

1B 6C... <ESC> “1"... 27 108... Draw/Erase/Complement a line 1B 6F... <ESCD “ol... 27 LI... Draw/Erase/Complement a circle 1B 6D... <ESC> “m"... 27 109... Move cursor to X,Y

1B 77 <ESC> “wi. 27 119 Fill a polygon

IB 64... <ESC> “d"... 27 100... Graphics screen dump Keyboard

iB 3h... <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> “LE” 27 116 69 Enable clock display

1B 74 44 <ESC> “tb” 27 116 68 Disable clock display

1B 74 3F <ESC> “t?” 27 116 63 Return clock time

Miscellaneous IB 61... <ESC> “a"... 27 97... Set/reset attributes

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

Page 22 of 51