Atari ST series Technical Reference Manual page 53

XBIOS Device and System Functions
Since the location of the default tables may change from ver­
sion to version of the TOS ROMs, the XBIOS includes the
Bioskeys() function, which allows you restore the default ta­
bles wherever they may be located. The syntax for this func­
tion is:
Bioskeys();
Software developers should be aware that Atari has writ­
ten a program called DEADKEYS.PRG, that allows the addi­
tion of foreign characters to the keyboard without remapping
the current key assignments. This program adds itself to the
beginning of the BIOS trap handler and checks to see if cer­
tain accent keys are struck. If they are, a flag is set so if the
next key pressed is a vowel, the vowel is printed with the
accent mark over it. The DEADKEYS.PRG program is avail­
able from Atari to registered software developers.
Screen Printing
TOS provides a screen print function. Whenever you press
the Altemate-Help key combination, or choose the Print
Screen menu item from the Options menu of the Desktop,
the ST sends commands to the printer that cause it to print
a graphic representation of the screen display, providing it's
the right type of printer (Atari- or Epson-compatible) and it's
properly installed (see Setprt() function, above). This same
function can be performed under software control, by the
XBIOS routine Scrdmp(), which is called from C by the pro­
gram statement
Scrdm p();
As stated above, the default screen print routine only
supports Atari and Epson-compatible dot-matrix printers.
The ST screen print function can, however, be made to work
with other printers by installing specialized printer drivers.
To accommodate this, the Scrdump() routine is vectored
through location 1282 ($502). This means that when
Scrdump() is called, or the Alt-Help keys are pressed, pro­
gram execution is directed to the routine whose address is
found at that location. To install a printer driver for another
printer, therefore, simply load the new screen print program
as a Terminate-and-Stay-Resident program (see Ptermres(),
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