Path: utzoo!utgpu!water!watmath!clyde!att-cb!att-ih!pacbell!amdahl!drivax!alexande
From: alexande@drivax.UUCP (Mark Alexander)
Newsgroups: comp.sys.ibm.pc
Subject: Re: GRAFTABL.COM: how do I detect if it is loaded?
Summary: You CAN use CGA characters on Hercules
Message-ID: <3290@drivax.UUCP>
Date: 30 Mar 88 18:14:08 GMT
References: <942@rmi.UUCP> <1635@ncsuvx.ncsu.edu>
Reply-To: alexande@drivax.UUCP (Mark Alexander)
Organization: Bob-ist Temple of Monterey
Lines: 30

In article <1635@ncsuvx.ncsu.edu> sam@ncsuvx.UUCP (Sam "SammyBake" Moore) writes:
>On a Hercules graphics card in graphics mode you use the ASCII character table
>in ROM? What mode are you working in and what Herc card is it? Can you explain
>how you use this table? I assumed this table would be useless to you in the
>(720 x 348) 2 color Hercules mode. 

In the BIOS ROM of a true blue PC (don't know about clones) there is a
font table of 8x8 characters for the CGA card.  It's used by the BIOS
when you switch into graphics mode on the CGA.  You can also use this
font table on the Hercules monochrome graphics card when it's in
graphics mode.  You get 43 rows of 90 columns each.  It looks a bit
crude (like the CGA), but it's readable.  I recently modified
MicroEMACS to use this mode, and it's great for editing programs --
you can see nearly twice as much stuff on the screen at once.

The table is located at F000:FA6E in the PC's I've used.  This appears
to a constant, since it's the same in both an ancient PC and an AT.  I
can't find any pointer to it in the interrupt page.

The problem with the ROM table is that it only covers characters
0-7Fh.  The purpose of GRAFTABL.COM is to supply the rest of the
characters (80h-FFh).  Interrupt vector 1Fh is used as a pointer to
this upper font table.

If anyone is interested in some assembly code that uses the ROM font
table (specifically, the code that I use in MicroEMACS), I'd be happy
to email it.
-- 
Mark Alexander	(UUCP: amdahl!drivax!alexande)
"Bob-ism: the Faith that changes to meet YOUR needs." --Bob