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Increasing Spatial Method for Accelerating Keystroke Action

IP.com Disclosure Number: IPCOM000046315D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 4 page(s) / 63K

Publishing Venue

IBM

Related People

Murphy, AS: AUTHOR

Abstract

An accelerating mode of operation is described for the keystroke action on alphanumeric or text keyboards for display terminals. This gives increased user performance for such operation as cursor control, ruling and deleting characters. Two different implementations are possible, the Decreasing Time Interval method and the Increasing Spatial Interval method. The latter method is described herein.

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Increasing Spatial Method for Accelerating Keystroke Action

An accelerating mode of operation is described for the keystroke action on alphanumeric or text keyboards for display terminals. This gives increased user performance for such operation as cursor control, ruling and deleting characters. Two different implementations are possible, the Decreasing Time Interval method and the Increasing Spatial Interval method. The latter method is described herein.

The velocity or rate profile for conventional keystroke action is shown as a dashed line in Fig. 1. It is seen that this technique employs a delay time of about 500 milliseconds ('Td') followed by a character generation rate of, for example, 10 Hz. The user is easily able to track a much higher velocity on a display screen and often desires to have a faster rate.

The accelerating keystroke action is shown by the solid line in Fig. 1. By correct attention to the human factors aspects of the tracking task it is possible to provide a higher maximum keystroke rate, for example, up to 50 characters/sec. At this rate it is important to present a smooth velocity profile to the user and to respond immediately at the 'key-break' instant. The value 'Te' should preferably be a constant small value and ideally equal to zero. As the constraint upon maximum character rate is now governed by the ability of the user to visually track the typing action, it is important to pay more attention to the provision of good visual feedback. This means that screen update should occur smoothly and jitter-free, and there should be as little delay as possible in responding to the user's actions (i.e., make and break of keys).

In CRT displays the video refresh cycle determines the time instants when new screen information can be presented to the user. Thus for simplicity the update rate may be made equal to the CRT frame refresh rate. Other rates and in particular sub-multiples of the frame rate may be selected, but these will result in reduced human factors on CRT terminals. For matrix addressed displays the update rate can be selected without this constraint.

Consider first the accelerating graphic pel (picture element) cursor. Let the initial velocity be 0, the acceleration be 80 pels/ sec2 and the update time interval be 25 msecs, that is, for a frame rate of 40 Hz. The distance the cursor is moved is given by the equation: Distance (pels) = (Acc x Time2)/2

for example:

Time Distance

(secs) (pels)

0.5 10

1.0 40

1.5 90

2.0 160

2.5 250

The update mechanism for a real implementation is shown in Fig. 2. Here, the pel position, acceleration and velocity values are represented with both fractional and integer parts, although update to the screen is in terms of integer

1

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pel positions only. The state of the key is sampled every refresh frame so that when a cursor control key is depressed, the cursor velocity is increased by 0.05 pel/frame for every refresh frame. Because the pel position is rounded ac...