Windows Resource Kit HDC Memory Viewer and Windows 3.0

• Microsoft Windows operating system versions 3.0, 3.0a

SUMMARY

The hDC Memory Viewer is a utility included as part of the Windows Resource Kit. This utility gives you a graphic display of how your system's memory (including extended and expanded memory) is being used. It also uses an icon to display the amount of free memory you have available. The following is a description of how Memory Viewer reports the memory usage under Windows.

MORE INFORMATION

The amount of memory use being reported in the DOS area includes the memory used by any TSR (terminate-and-stay-resident) programs and drivers, including SMARTDrive or RAMDrive.

When the Include Discardables check box is selected in the Options File menu in the hDC Memory Viewer, it will display the sum amount of memory including code segments that Windows has marked as "discardable." Not all the code segments that an application requires are needed at any given moment. When these unused code segments are marked as discardable, Windows can use that area of memory for another applications. However, it must always save enough memory space so that all the applications that are loaded can perform any potential functions that they might call. This is where the "Swap Area" listed on the Memory Viewer comes in; this is a common "ensure area" that Windows uses to ensure that all applications have the potential memory that they may need.

Most Windows-based applications have a large portion of their code segment marked as discardable; however, not all Window's-based applications do this.

The Memory Viewer has the option to display memory used by applications, system libraries, system fonts, and device drivers. The memory reported in use by system libraries (User, GDI, and so on) is an indication of how much system resources are being used, but it requires some interpretation. The amount reported for each library includes the data segment, any code segments, and any objects on the local heap "owned" by that library. Any one of these items can be up to 64K (thus the 64K limitation on system resources in Windows 3.0). When combined, however, they could be a lot more -- this is why each of the libraries can total 100K or more.

REFERENCES

hDC Corp. Technical Support

"Windows Resource Kit," page 173