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Browse Prior Art Database

Client/Server Intra-Operability between Disk Operating System Boxes

IP.com Disclosure Number: IPCOM000111295D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Alward, WA: AUTHOR [+6]

Abstract

Disclosed is the capability for DOS and Windows* programs on a PC under the OS/2* operating system in a Virtual DOS Machine (DOS BOX) to access DOS Resources in another DOS session, effectively increasing the capabilities of DOS.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Client/Server Intra-Operability between Disk Operating System Boxes

      Disclosed is the capability for DOS and Windows* programs on a
PC under the OS/2* operating system in a Virtual DOS Machine (DOS
BOX) to access DOS Resources in another DOS session, effectively
increasing the capabilities of DOS.

      The OS/2 2.1 operating system has supplied a new capability
which allows a user to run multiple DOS boxes simultaneously.  This
capability virtualizes all resource and hardware accesses that are
made from each DOS box and protects the OS/2 operating system from
crashing.

      In addition, if an application running in one of these DOS
boxes crashes, OS/2 2.1 protects all other DOS boxes from being
effected.

      In other words, OS/2 2.1 protects each DOS box from another and
lets the user run these boxes concurrently.

      Another feature of the OS/2 operating system is the concept of
a virtual DOS device driver (VDD).  This is an OS/2 program that
provides an API to allow the creation of hooks or stubs in each DOS
box.

      For example, you can hook a software interrupt, so that anytime
a DOS program issues a software interrupt, your program will get
notified in the virtual DOS device driver code, of which DOS box has
issued the interrupt, and your program will get control in the VDD.

      This means that from an OS/2 VDD program you can manipulate
each DOS box program whenever a software interrupt is issued.

      For this invention, the program hooks INT68 in each DOS box.
Whenever a DOS client application wishes to use the client/server
APIs described above, the program should set up pointers in DOS
memory and issue a software INT68.

      When the OS/2 VDD program gets control it then copies the
command from one DOS box memory area of the client application to the
DOS box area of the DOS server application.  By using standard OS/2
semaphores, the OS/2 VDD prevents two clients from calling at the
same time.  (Semaphores are a way in which a shared resource is
blocked from one application during critical processing.)

      The DOS box server application is woken up from the OS/2 VDD
program whenever a DOS box client program has a request to be
processed.

      When the DOS box server application completes processing the
request, it issues a software interrupt to let the OS/2 VDD know it
is complete.  The OS/2 VDD then unblocks the mutex semaphore to let
the next DOS client's request go to the DOS box server, and then on a
separate execution thread returns the processing results of the first
...