Apple II
Technical Notes
_____________________________________________________________________________
                                                  Developer Technical Support
GS/OS
#14: The Console Driver Technical Note

Written by: Matt Deatherage                                          May 1992

This Technical Note discusses the GS/OS Console Driver and related issues.
_____________________________________________________________________________


NEW 6.0 CHARACTER FEATURES DON'T WORK IN VERSION 3.2

The System Software 6.0 documentation (as of this writing, the GS/OS ERS)
refers to a new Console Driver feature.  The Console Driver now has the
capability to return direct character-in and character-out vectors for
improved throughput (gained by bypassing most of GS/OS's overhead).  The
vectors are obtained through new DStatus device-specific call $8007,
GetVectors.

Unfortunately, in version 3.2 of the Console Driver (which ships with System
Software 6.0), this call returns addresses which are almost the correct ones
(in other words, they're wrong).  If DInfo says the Console Driver is version
3.2 or earlier, don't try to use the GetVectors feature.


NO-WAIT MODE AND USER INPUT MODE CONFLICT

When you read from a GS/OS driver in no-wait mode, the driver is supposed to
return as quickly as possible, reading as much information as possible and
returning as soon as the request is filled or no more information is instantly
available.  This is the opposite of wait mode, where the driver waits until
the read can be finished even if it takes forever.

This philosophy directly conflicts with the Console Driver's user input
routine (UIR) mode, where standard human interface editing functions are
available.  For example, if you want to read seven characters from the Console
Driver in UIR mode, the user should be able to type four characters and hit
three backspaces and not worry that the read request will end since he pressed
seven keys.  The entire concept of UIR mode is that the user can take his time
and edit his input until he's happy with it, then press a terminator key to
end editing.

This is how the Console Driver works, in fact, even in no-wait mode.  If you
ask for even one character in UIR mode and no-wait mode, the Console Driver
will let the user edit the one character until he presses a terminator.

If you want instant feedback, you must use raw input mode.


Further Reference
_____________________________________________________________________________

   o   GS/OS Reference
   o   System 6.0 Documentation for GS/OS