Patent
1992-11-24
1998-04-21
Bost, Dwayne
395110, G06K 1500
Patent
active
057427461
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a character output control method and apparatus for controlling from a host system the operation of outputting a character to a terminal, such as character display unit or printer, which has character pattern memory region for storing character patterns.
BACKGROUND ART
A terminal, such as display terminal or printer, of the character cell type has the function of displaying or printing a character pattern loaded from a host system or storing the character pattern in a character pattern memory region which is controlled as a cache (hereinbelow, the memory region shall be termed the "character pattern cache"). Techniques which control the operation of outputting a character to the terminal have heretofore been as follows:
Software for controlling the terminal transmits character codes to-be-output to the terminal irrespective of whether or not the terminal has stored the character patterns. On this occasion, in a case where the terminal has not stored the character pattern, it notifies the software of the necessity of the character pattern. This shall be called the "character pattern request of the terminal". The notified software temporarily suspends the operation of outputting remaining characters, and it loads the requested character pattern corresponding to the character code and causes the terminal to display or print the character pattern, whereupon it restarts the operation of outputting the remaining characters. This technique shall be called the "on-demand character pattern loading technique based on hardware" in order to contrast it with the present invention.
All the character patterns which the user of the terminal requires are collectively loaded in the terminal beforehand, whereby character pattern loading is dispensed with in the subsequent operation of outputting characters. This technique shall be called the "collective preloading technique" in order to contrast it with the present invention.
In the prior-art technique (a), the on-demand character pattern loading technique based on hardware as stated above, there is the problem that the form and method in which the terminal is connected are limited. More specifically, in case of using this technique, the terminal 1 must be kept in direct connection with the host system 2 which has the character pattern loading control function as stated before, as shown by Connection Form 1 in FIG. 4 of the accompanying drawings. In other words, in a case where the terminal 1 is connected through another host system 3 such as a host system which does not have the character pattern loading function, as shown by connection Form 2 in FIG. 4, this technique cannot be used. Besides, in the connection of the terminal 1 through a terminal server device 4 or the like as shown by Connection Form 3 in FIG. 4, the communication protocols of the terminal server device 4 and between the terminal server device 4 and the host system 2 need to be expanded.
On the other in the prior-art technique (b) as stated above, there is the problem that the number of the character patterns which can be collectively loaded is limited by the size of the character pattern reserving zone of the terminal.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a character output control method and apparatus for a terminal which can eliminate the aforementioned problems of the prior-art techniques.
According to an aspect of the present invention there is provided a character output control method for controlling from a host system an operation of outputting a character to a terminal, such as character display unit or printer, which has a character pattern memory region for storing character patterns, said method comprising the steps of, in case of outputting a desired character to said terminal, firstly examining at the side of said host system whether or not a character pattern corresponding to the desired character is stored in said character pattern memory region, and secondly loading the character pattern fr
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Doi Hitoshi
Okutsu Masayoshi
Bost Dwayne
Digital Equipment Corporation
Drozenski Diane C.
Hudgens Ronald C.
Legree Tracy M.
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