Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

  ◄Memory and Capacity►                          ◄Contents►  ◄Index►  ◄Back►
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Overview of Memory Management
Together, ISAM and QBX require over 450K to run, leaving memory sufficient
to develop programs of moderate-size. Fortunately, you can use a variety
of techniques to make more memory available for program use:
 
  ■  The /Nofrills command-line option reduces the memory QBX uses by 19K.
     This option reduces some functionality, but requires no special memory
     boards or device drivers.
 
  ■  If you have extended memory, you can move about 60K of the QBX
     executable code from conventional memory into extended memory,
     freeing this memory for program use.
 
  ■  If you have expanded memory, you can use up to about 1.2 Mb of expanded
     memory for ISAM buffer space, freeing a significant amount of
     conventional memory.
 
     With expanded memory, you can also move certain kinds of program code
     and data out of conventional memory. The amount of code and data moved
     depends on how you write your program and what command-line options
     you give. ◄Using Expanded Memory► explains these considerations.
 
Extended Memory - Description
The Extended Memory Specification (XMS) version 2.0 is a convention that
allows applications to access a 64K segment of extended memory located just
above the 1 MB memory address. This particular segment of extended memory
is called the High Memory Area (HMA) and is accessed with the device driver
HIMEM.SYS. With a memory board installed and recognized by your computer,
the microprocessor treats the HMA as an extension of RAM.
 
Extended memory can be used only on machines that use an 80286 or later
microprocessor chip. The IBM PC, IBM XT and compatible machines cannot
use extended memory because the 8088 and 8086 microprocessor chips used
in these machines cannot address memory beyond the 1 Mb address.
 
If you have an EMS (Expanded Memory Specification) board, you may be able
to allocate part of its memory (64K is the recommended optimum amount)
to extended memory by reconfiguring the board and leaving the rest as
expanded memory. Refer to your EMS board manual for more information about
reconfiguring your board.
 
Expanded Memory - Description
Expanded memory is supported by the Lotus/Intel/Microsoft Expanded Memory
Specification (LIM EMS) version 4.0, and is accessed via expanded memory
managers (EMM), such as the QEMM.SYS, MEMM.SYS, and CEMM.SYS device drivers,
as well as by Windows 386. The 386MAX.SYS EMM provides additional expanded
memory support, described below.
 
The 386MAX.SYS expanded memory device driver, by Qualitas, offers the most
complete memory support for computers that run on 386 and later processors.
It is an expanded memory emulator that allows access to the HMA and
possibly to conventional memory for memory-resident programs and certain
other programs.
 
A number of extended memory drivers can utilize some or all extended memory
to emulate expanded memory. Use an expanded memory emulator only if you
have no expanded memory hardware. All information in "QBX Memory and
Capacity" regarding expanded memory hardware applies to expanded memory
emulators as well.
 
To use expanded memory, you must have an expanded memory device driver set
in your CONFIG.SYS file. Only one expanded memory device driver can run
on the system. (You must reboot for changes in your CONFIG.SYS
file to take effect.) Alternatively, you can simply run Windows 386
if you have it installed.
 
  See Also    ◄Using Extended Memory►
              ◄Using Expanded Memory►