Browse Prior Art Database

DOS Extender Execution Environment for Related Applications

IP.com Disclosure Number: IPCOM000102332D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Manges, MG: AUTHOR [+3]

Abstract

A method for allowing related applications to share DOS Extender kernel code is disclosed. This allows these related applications to share code and data while minimizing conventional memory requirements.

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

DOS Extender Execution Environment for Related Applications

       A method for allowing related applications to share DOS
Extender kernel code is disclosed.  This allows these related
applications to share code and data while minimizing conventional
memory requirements.

      The PC DOS operating system has an addressability limit of one
megabyte of memory.  Of this one megabyte, 640K of it is usable by PC
DOS and applications.  This addressable memory area is referred to as
conventional memory.  Memory requirements for all applications seem
to grow as they are enhanced and become more sophisticated.

      To alleviate the conventional memory problem, some products
have used DOS Extenders.  This technology allows the PC Support
resident code to be placed and executed in extended memory (memory
above 1 megabyte on Intel 80286+ based computers).  When this code
needs to be executed, the processor is switched into Protected Mode
so this extended memory is directly addressable.  The processor is
switched back to Real Mode after the application has completed
performing its function.

      A program is required to link with the DOS Extender library
routines to use extended memory.  The problem with this approach is
that even though a DOS Extender allows a program to be placed and
executed in extended memory, each invocation of a Protected Mode
program takes up a sizable amount of conventional memory for the DOS
Extender kernel code itself.

      Besides using conventional memory, each DOS Extender enabled
application has its own execution environment.  This means that the
DOS Extender kernel code cannot be shared easily with other DOS
Extender enabled programs.  Thus, each application has its own
execution environment, which, in turn, makes it very difficult to
share code and data in extended memory with other applications.  But
if a program is not linked with the DOS Extender library, it cannot
execute in Protected Mode or access the DOS Extender kernel code to
use extended memory functions.

      Instead of linking separate applications with the DOS Extender
library, a new approach was used.  A PC Memory Manager program was
written which solves the DOS Extender problem.  In thi...