Obtaining Memory Statistics & System Resources

Extract information about the current state of the system’s memory using the GlobalMemoryStatus API function. An application can use this function to determine how much memory it can allocate without severely impacting other applications.

Windows 9x still uses Windows 3.x system resource structure which is two 64KB sections of memory set aside for specific jobs. The GDI (Graphics Display Interface) section stores fonts, bitmaps, etc for on-screen display. When an application runs, parts of the User resources section go to their menu lists, window logistics, and other information. Whenever you start a program it uses some system resources but doesn't always release them when it closes. Eventually, resources diminish until you reboot Windows.

You can determine the values that show up in the Resource Meter or that are displayed in Explorer's Help About dialog by using the Resource Meter's Rsrc32.dll. Again, you can check the system resources before you shell to another application. If the resources dip below a given value you can issue a warning message.

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Determining the System Resources only applies to Windows 9x machines.

You can determine the memory statistics listed in the following table by calling the GlobalMemoryStatus API function. This function takes a single parameter which is the MemoryStatus structure defined below. GlobalMemoryStatus populates the structure with the memory values.

   Type MEMORYSTATUS
      dwLength As Long        ' sizeof(MEMORYSTATUS)
      dwMemoryLoad As Long    ' percent of memory in use
      dwTotalPhys As Long     ' bytes of physical memory
      dwAvailPhys As Long     ' free physical memory bytes
      dwTotalPageFile As Long ' bytes of paging file
      dwAvailPageFile As Long ' free bytes of paging file
      dwAvailVirtual As Long  ' user bytes of address space
      dwTotalVirtual As Long  ' free user bytes
   End Type

On 9x systems you can obtain System Resource information by calling the pBGetFreeSystemResources function in Rsrc32.dll. This dll does some thunking and uses Rsrc16.dll. Due to the 16-bit nature of this function, it is not available on the 32-bit NT and Windows 2000 operating systems.

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