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Official Statement For The Sticking Shift Key
DocumentID: 633418
Revision Date: 29-Feb-96 3:03:15 PM

The information in this document applies to:
WordPerfect® 5.1 for DOS

Problem

Solutions: FYI:
After considerable testing, PC Development has determined that the Sticking Shift Key problem is in the BIOS of some machines. It can also be caused by Terminate and Stay Resident (TSR) programs. Customers should clearly understand that it is not a WordPerfect problem. However, WP has modified WordPerfect 5.1 for DOS in the interim dated 03/09/92 to work around most, but not all, sticking shift key problems.

When the Shift key is pressed, the keyboard sends scan codes to the computer. An interrupt routine in the BIOS (Basic Input/Output System) processes the scan codes. Some keyboard handler's enable interrupts without disabling the keyboard. If another scan code is received while the BIOS is servicing another interrupt (e.g., the timer), the first scan code is overwritten and lost, and the next scan code is interpreted as a non-enhanced keystroke (a shift key or numeric key). DOS then assumes the Shift key is down.

See memo EDT_070 for more information.

Answer:

Details:


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