Path: utzoo!attcan!uunet!husc6!think!bloom-beacon!mit-eddie!rutgers!att!lzaz!mtunb!dmt
From: dmt@mtunb.ATT.COM (Dave Tutelman)
Newsgroups: comp.sys.ibm.pc
Subject: Re: US PC programmers still live in a 7-bit world!
Summary: ...and INT for PC special font
Message-ID: <1257@mtunb.ATT.COM>
Date: 12 Jul 88 12:30:43 GMT
References: <1988Jun22.223158.1366@LTH.Se> <699@omen.UUCP> <1288@odyssee.UUCP> <29@cybaswan.UUCP>
Reply-To: dmt@mtunb.UUCP (Dave Tutelman)
Organization: AT&T Information Systems - Lincroft, NJ
Lines: 33

In article <29@cybaswan.UUCP> iiit-sh@cybaswan.UUCP (s.hosgood) writes:
>Can you reprogram the character set in an IBM-PC to put in the characters you
>want?? Rumour has it that INT $1F points to a table of characters with codes
>$80 - $FF. It seems to be ignored on my clone-XT (monochrome adaptor fitted).

Yes, but ONLY for graphics adapters (NOT the alphanumeric monochrome) in
graphics mode (NOT in character mode).

The table is a set of bitmaps (e.g. - eight 8-bit bytes per character for
the CGA, giving an 8x8 bitmap) for displaying characters 0x80 to 0xFF.
You can create any graphics you want within the constraints of:
   -	A standard character station is the only "brush" supported.
   -	Only 128 shapes supported.
   -	Must be used in graphics mode (which can be slow, and is not
	standard for most text-based systems).

Why for graphics mode only?  Because the character-only display adapters
have on-board ROM to define the characters.  (This may be changed for
some of the new adapters; I understand the NEW Hercules has downloadable
fonts.)  Only in the graphics mode, where the BIOS draws characters
pixel-by-pixel, is the font under software/firmware control.

>                       Steve Hosgood BSc,
>             Innovation Centre, University of Wales,
>                         Swansea SA2 8PP
>    Phone (0792) 295213		JANET: iiit-sh@uk.ac.pyr.swan

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