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  Copyright © 1997 Mark Russinovich and Bryce Cogswell

  Last Updated July 9, 1997

  VCMon - Windows 95 VCache (disk cache) Monitor

    Introduction VCMon is a Windows 95 VxD/GUI combination that appeared
                 in our May, 1996 Dr. Dobb's Journal article, "Examining
                 VxD Service Hooking". While its primary goal is to serve
                 as a demonstration of the interesting things that can be
                 monitored easily with service hooking, disk cache
                 monitoring can be useful and informative in its own
                 right. In addition, the graphs that VCMon implements may
                 be useful in your own programs.

    Installation Install VCMon by copying Vcmon.vxd and Vcmon.exe to the
         and Use same directory on your hard drive, and start it by
                 running Vcmon.exe from that directory. The GUI
                 dynamically loads the virtual device driver (VxD), which
                 starts watching disk cache activity. The checkboxes can
                 be toggled to pop open graphs that represent recent
                 activity.

          Sample This is a screenshot of VCMon watching disk cache
      Screenshot activity.

       How VCMon The heart of VCMon is in the virtual device driver,
           Works Vcmon.vxd. It is dynamically loaded, and in its
                 initialization it installs VxD hooks for disk cache, as
                 well as page faulting services.

                 Periodically (at a rate that can be controlled through
                 the dialog), the GUI asks the VxD to fill in a data
                 structure with the current statistics, which are then
                 used to update the dialog box and the graphs.

            More The following serve as additional sources of information
     Information on the Windows 95 VxD hooking:

                    * The Windows 95 DDK
                    * "Examining VxD Service Hooking," by Mark
                      Russinovich and Bryce Cogswell, Dr. Dobb's Journal,
                      May 1996
                    * "Systems Programming for Windows 95," by Walter
                      Oney, Microsoft Press, 1996 (a must have for VxD
                      writers)

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                           Download VCMon (39KB)

                     Download VCMon Plus Source (107KB)

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