Browse Prior Art Database

Monitor for Multikey Sequence

IP.com Disclosure Number: IPCOM000100534D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 95K

Publishing Venue

IBM

Related People

Morse, RK: AUTHOR [+2]

Abstract

This algorithm detects a specific two-keystroke sequence on personal computers. The defined keystroke sequence consists of having two target keys being pressed in a specified order and then releasing both target keys with no other keys being pressed or released during the keystroke sequence. This algorithm solves the problem of detecting a proper keystroke sequence by taking into account both the key make and break scan codes instead of only the key make scan codes. This algorithm allows the computer program to process according to whether the proper keystroke sequence was detected or not.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Monitor for Multikey Sequence

       This algorithm detects a specific two-keystroke sequence
on personal computers.  The defined keystroke sequence consists of
having two target keys being pressed in a specified order and then
releasing both target keys with no other keys being pressed or
released during the keystroke sequence.  This algorithm solves the
problem of detecting a proper keystroke sequence by taking into
account both the key make and break scan codes instead of only the
key make scan codes.  This algorithm allows the computer program to
process according to whether the proper keystroke sequence was
detected or not.

      Computer programs take control of various hardware resources.
One of these available hardware resources on personal computers is
the keyboard.  Computer programs can take control of the keyboard by
intercepting all interrupts generated whenever a key is pressed or
released.  These keyboard interrupts generate unique values, called
scan codes which, in turn, indicate which key was pressed or
released. The downward press of a key is referred to as a key make.
The upward release of a key is referred to as a key break.  Personal
computer keyboard hardware continues to generate key make scan codes
while a key is being held. This repetition is referred to as the
keyboard typematic function.

      This algorithm solves the problem of detecting when the proper
key sequence has been generated by waiting for the second key break
after the proper key makes and first key break was received without
any extraneous key makes or key breaks in between.  This algorithm
also negates the problem presented by personal computers' typematic
function.  High performance and low memory usage of this algorithm
was also critical since the sequence monitoring occurs during
real-time keystroke handling.

      The algorithm is defined to take advantage of the requirements
that the keys must be pressed in a very specific sequence with no
extraneous keystrokes allowed during the sequence.  This algorithm
detects the sequence A B A' B' where...