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DCBS Print Function in DOS LAN Requester Disclosure Number: IPCOM000105875D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20

Publishing Venue


Related People

Ohta, M: AUTHOR [+1]


Disclosed is a programming concept for DBCS, enabling the print function in the DOS LAN Requester*.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 18% of the total text.

DCBS Print Function in DOS LAN Requester

      Disclosed is a programming concept for DBCS, enabling the print
function in the DOS LAN Requester*.

      INT 17H had to be hooked and modified to also include
additional DBCS print subfunctions.  INT 5H had to be hooked to know
PRINT AND UNLOADED only when PS/55 hardware is in use.

      PS/55 Print support is introduced to allow all users working
with DBCS DOS to get the same benefit from DOS LAN Requester as users
working with PC-DOS.

      Because DBCS DOS has some deviations from PC-DOS in BIOS
hardware- dependent functions, DOS LAN Requester could not achieve
all its functions, especially, printer-related functions with DBCS

      PS/55 Print support adapts DOS LAN Requester to DBCS DOS BIOS
functions dynamically (this means, changes to DOS LAN Requester
itself are not required.), and enables DOS LAN Requester to work
correctly with DBCS DOS also.

      This document specifies the functions that PS/55 Print should
satisfy.  One of important roles of DOS LAN Requester is to enable
DOS users to use remote resources such as disks and printers that are
attached to servers across networks.  To achieve this role, DOS LAN
Requester intercepts all I/O requests at the DOS function level (int
21h) and redirects them to a remote.  Furthermore DOS LAN Requester
also redirects PS/2 printer BIOS calls (int 17h) to a remote because
most of popular DOS applications use PS/2 printer BIOS calls instead
of DOS function calls mainly for performance improvement.

      But this means that DOS LAN Requester tightly depends on PS/2
printer BIOS functions.  Therefore, DOS LAN Requester cannot work
with any other DOSs than PC-DOS and the DOS whose BIOS is 100%
compatible to PC-DOS.

      This was one of the reasons why DOS LAN Requester was not
supported in Japan and the AP countries.  DBCS DOS 4.x, which is used
in Japan and the AP countries, is built on the PS/55 "conventional"
BIOS (EBIOS or EPOCH BIOS) that has been used since the first PS/55
(IBM 5550, EPOCH) was put on the Japanese market in 1983.  As "old"
PS/55 was quite different from PS/2 (or IBM PC/XT/AT*), EBIOS is also
different from PS/2 BIOS to support the "old" PS/55' uniqueness.  In
fact, EBIOS has 6 additional printer-related functions compared with

      That is, the DOS LAN Requester cannot handle these EBIOS
additional printer- related functions.  PS/55 Print Support
(PS55PRINT) is designed and implemented to solve this situation.
PS55PRINT incorporates with DOS LAN Requester as a network service
and allows a user working with DBCS DOS 4.x to redirect EBIOS calls
to a remote, just the same as a user working with PC-DOS.

      Actually, PS55PRINT is a "terminate and stay resident" (TSR)
type executable and loaded after DOS LAN Requester's redirector
component.  And once it is loaded, it interprets EBIOS...