Basic Disk Operating System (BDOS) Functions
Upon
entry to function
6,
register D L contains either (1) hexadecimal
FF,
denoting
a
CONSOLE input status request, (2) hexadecimal
FE,
denoting a CONSOLE
status request,
or
(3)
an
ASCII character to be
output
to CONSOLE, where
CONSOLE
is
the logical console device.
•
If
the input value
is
FF,
function· 6 directly calls the BIOS console input
function.
If
a character
is
ready,
it
is
returned in AL; otherwise a zero
is
returned in AL.
•
If
the input value
is
FE,
function 6 returns zero in register AL
ifno
character
is
ready,
and
FF
in register AL otherwise.
•
If
the input value in
DL
is
not
FE
or
FF,
function 6 sends the ASCII
character in
DL
to the console.
Do
not
use function 6 (with
FE
of
FF)
in combination with either function 1
or
function
2.
Function 1 should be used in conjunction with function
2.
Function 6
must be used independently.
GET
I/O
BYTE
ENTRY
RETURN
CL:
07H
FUNCTION 7
AL:
I/O
Byte Value
GET
I/O
BYTE
The
Get
I/O
Byte function returns the current value
of
10BYTE
in register AL.
When the
10BYTE facility
is
implemented in the BIOS, IOBYTE contains the
current assignments for the logical devices CONSOLE, READER,
PUNCH,
and
LIST.
NOTE
CBIOS supports this call dynamically for the
LIST device only (see Chapter 5). However,
the call may be used in programs
that
operate
with standard
CP/M
calls to the BIOS.
4-7
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