User`s guide

bit 3 : This bit disables all CTRL-C intercept action in the BDOS. This mode is
useful for programs that must control their own termination.
bits 8 and 9 : The BDOS does not use these bits, but reserves them for the CP/M 3
GET RSX that performs console input redirection from a file. With one
exception, these bits determine how the GET RSX responds to a program
console status request (Function 6, Function 11, or direct BIOS).
bit 8 = 0, bit 9 = 0 - conditional status
bit 8 = 0, bit 9 = 1 - false status
bit 8 = 1, bit 9 = 0 - true status
bit 8 = 1, bit 9 = 1 - do not perform redirection
In conditional status mode, GET responds false to all status requests except for a
status call preceded immediately by another status call. On the second call, GET
responds with a true result. Thus, a program that spins on status to wait for a
character is signaled that a character is ready on the second call. In addition, a
program that makes status calls periodically to see if the user wants to stop is not
signaled.
When a transient program begins execution, the Console Mode bits are normally
set to zero. However,, the CP/M 3 utility GENCOM can attach an RSX header to a
COM file so that when it is loaded, the console mode bits are set differently. This
feature allows you to modify a program's console I/O behavior without having to
change the program.
2.2.2 Other Serial I/O
The BDOS supports single character output functions for the logical devices LST:
and AUXOUT:, an input function for AUXIN:, and status functions for AUXIN:
and AUXOUT:. A block output function is also supported for the LST: device.
Unlike the console I/O functions, the BDOS does not intercept control characters or
expand tabs for these functions. Note that AUXIN: and AUXOUT: replace the
READER and PUNCH devices supported by earlier versions of CP/M.
2-6Pb
2.3 BDOS File System
2.2 BDOS Serial Device I/O CP/M 3 Programmer's Guide