Browse Prior Art Database

Device for Buffering Keyboard Input on the IBM 3277

IP.com Disclosure Number: IPCOM000049472D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Capek, PG: AUTHOR [+2]

Abstract

In using IBM 3277 terminals characters typed at the keyboard are not buffered in the head. Since the terminal is connected to the host machine via a simplex line, characters typed while the head is not listening to the keyboard are lost. This occurs if the host is transmitting to the terminal, or the terminal is in input inhibited mode.

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Device for Buffering Keyboard Input on the IBM 3277

In using IBM 3277 terminals characters typed at the keyboard are not buffered in the head. Since the terminal is connected to the host machine via a simplex line, characters typed while the head is not listening to the keyboard are lost. This occurs if the host is transmitting to the terminal, or the terminal is in input inhibited mode.

This characteristic of the terminal is extremely annoying for touch typists, since they must watch the screen to be sure the machine saw what they typed, or fast typists issuing a sequence of commands to the host. For example, the host typically responds with some return message after each command (e.g., in CMS: R; <time>). These responses cause characters of the command line currently being typed to be lost.

To alleviate this shortcoming, a FIFO (first-in, first-out) queue can be interposed between the keyboard and the head, as shown in Fig. 1. Characters enter the FIFO queue provided the queue is not full. If the FIFO is full, the characters are lost. Characters are sent from the queue to the head provided the head is listening. Should the head not be listening, the queue will start to fill up.

Fig. 2 shows a particular implementation of this scheme with 3277s. The queue is of length 32, allowing the typist to type about half a line without the head accepting any of the characters before any characters are lost.

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