Memory Required by Extended FoxPro Version 2.0

 Last reviewed: April 17, 1995
Article ID: Q86906
The information in this article applies to:
  • Microsoft FoxPro for MS-DOS, version 2.0

SUMMARY

The Extended Version of FoxPro version 2.0 can run on 386 and 486 computers with a minimum of 1.5 megabytes (MB) of extended memory. Use the Standard Version if less than 1.5 MB of extended memory is installed.

FoxPro will achieve better performance when the system has at least 2 MB extended memory installed.

Extended FoxPro is incompatible with Microsoft Windows operating system versions 3.0 and 3.1 running in 386 enhanced mode.

MORE INFORMATION

The Extended Version of FoxPro can use extended memory or expanded memory; however, it cannot use both simultaneously. If some extended memory is configured as expanded memory, FoxPro will access only the expanded memory.

FoxPro Extended Version (X) uses a modified version of the Ergo OS386 MS-DOS Extender to run in protected mode on a 386 computer. The MS-DOS Extender can operate in a variety of environments. When it starts, it checks for the following memory environments in the following order:

  1. A DPMI (MS-DOS Protected Mode Interface) server

    Enhanced mode Windows 3.0 and 3.1 are DPMI servers. Because Ergo OS386 does not support DPMI, FoxPro (X) does not load if a DPMI server is detected.

  2. A VCPI (Virtual Control Program Interface) server

    EMM386.EXE provided with MS-DOS 5, EMM386.EXE provided with Windows 3.0 or 3.1, 386MAX and BlueMax from Qualitas, QEMM-386 from QuarterDeck, and CEMM from COMPAQ are all VCPI servers.

  3. An XMS (Extended Memory Specification) driver

    HIMEM.SYS from Microsoft, HIMEM.SYS from COMPAQ, 386MAX and BlueMax from Qualitas, and QEMM-386 from QuarterDeck are XMS drivers.

  4. None of the above

    In this case, the OS386 calls Interrupt 15h directly to allocate and use extended memory.

Because enhanced mode Windows 3.0 and 3.1 are DPMI servers, FoxPro (X) does not run in an MS-DOS window in Windows. To work around this limitation, use Standard Version FoxPro with Windows 3.0 and 3.1 in enhanced mode, or use Windows 3.0 and 3.1 in standard mode and Extended Version FoxPro.

For more information, see pages 15-6 through 15-9 of the "Microsoft FoxPro Developer's Guide."

The servers and drivers listed above are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.

Additional reference words: FoxDos 2.00 3.00 3.10
KBCategory: kbenv kb3rdparty
KBSubcategory:

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Last reviewed: April 17, 1995
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