Microsoft KB Archive/250512

Knowledge Base

PRB: OS() Function May Not Return "NT" Under Windows 2000

Article ID: 250512

Article Last Modified on 10/15/2003

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APPLIES TO

• Microsoft Visual FoxPro 6.0 Professional Edition, when used with:
  • Microsoft Visual Studio 6.0 Service Pack 3

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This article was previously published under Q250512

SYMPTOMS

Code that tests the return value for the string "NT" of the OS() function in Microsoft Visual FoxPro 6.0 Build 8492 or later operates incorrectly under Microsoft Windows 2000.

CAUSE

Because Windows 2000 is not designated as "Windows NT," but is referred to as "built on NT Technology," the OS() function should no longer refer to it as "Windows NT 5.0."

RESOLUTION

There are two workarounds for this issue:

• Use the GetVersionEx Win32API call to return extended version information about Microsoft Windows, including the platform type. See the "References" section for more information on this function.

• Use the following code to test all possible return values from OS() in a DO CASE block to see which version you are running. However, this might require that the code be rewritten with each major Windows release.

  Clear
  Do Case
     * Tests for Windows 2000
     Case "5.00" $ OS()
     ? "Windows NT 5.0"
  
     Case "NT 4.00" $ OS()
     ? "Windows NT 4.0"
  
     * Tests for Windows 95
     Case "4.00" $ OS()
     ? "Windows 95"
     
     * Tests for Windows 98   
     Case "4.10" $ OS()
     ? "Windows 98"
  EndCase

STATUS

This behavior is by design.

MORE INFORMATION

The following code is typically written in programs that use API calls specific to a given operating system:

IF "NT" $ OS()
  *!* do NT-specific stuff
ELSE
  *!* do Win 9x-specific stuff
ENDIF
                

However, when testing for the presence of a particular feature, it is better to use the GetProcAddress API call. See the "References" section for more information.

Steps to Reproduce Behavior

1. Run Visual FoxPro 6.0 Service Pack 3 under Windows NT 4.0. Type  ? OS() in the Command window, and note that it prints "Windows NT 4.0."
2. Run Visual FoxPro 6.0 (no service pack) under Windows 2000. Type  ? OS() in the Command window, and note that it prints "Windows NT 5.0."
3. Run Visual FoxPro 6.0 Service Pack 3 under Windows 2000. Type  ? OS() in the Command window, and note that it prints "Windows 5.0."

REFERENCES

For additional information about the GetVersionEx API call, click the article number below to view the article in the Microsoft Knowledge Base:

188987 HOWTO: Determine the Operating System Build Number

For additional information about calling the GetProcAddress function, click the article number below to view the article in the Microsoft Knowledge Base:

193573 HOWTO: Determine the Version of a DLL

Keywords: kbbug kbxbase kbprb KB250512

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