MEM 0070h:016Ch - DR-DOS 7.02-7.03 - "DEVNO" AUX/PRN PORTIBM PC Portable (uses same BIOS as XT) ASSIGNMENTS Size: 2 BYTEs 016Ch BYTE PRN: assignment (0..2 for LPT1:..LPT3: (3 for LPT4:); default: 1) 016Dh BYTE AUX: assignment (0..3 for COM1:..COM4:; default: 1) Notes: As long as the built-in AUX: or PRN: drivers are in effect, these settings can be transparently reassigned at the DR-OpenDOS 7.02 / DR-DOS 7.03 DOS BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware. The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. device driver level (that is below DOS redirection etc., but above ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware. The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly.) using the undocumentedInformation about a product which is not publicly available from the manufacturer, and must be determined by reverse-engineering (disassembly, trial-and-error, etc.). Undocumented information tends to change -- often dramatically -- between successive revisions of a product, since the manufacturer has no obligation to maintain compatibility in behavior which is not explicitly stated. CONFIG.SYS AUX=0|1..4 and PRN=0|1..3|4 directive, where 1..4 specifies COM1:..COM4: or LPT1:..LPT4: and the high speed bypass 0 selects the previous hardwired equivalence of AUX: with COM1: and PRN: with LPT1: at this level, saving a few clock cycles. The system defaults to AUX=1 and PRN=1 (that is 0 in the internal variables). If the high speed bypass was not enabled, the assigment can be changed anytime later by updating these bytes, e.g. by a future issue of the MODE utility. If the highspeed bypass has been enabled, changes have no effect. The LPT4 setting (or corresponding value 3) is valid for DR-OpenDOS 7.02 and DR-DOS 7.02, but due to a bug introduced with the partial removal of the LPT4: device, it must not be used under DR-DOS 7.03. The address 0070h:016Ch is only valid for DR-OpenDOS 7.02 up to DR-DOS 7.03 (BDOS 73h), and will most probably change with future releases of DR-DOS! These bytes are local for each task running. SeeAlso: INT 21h/03h, INT 21h/04h, INT 21h/05h, MEM 0040h:0000h etc.