CA1121061A - Method and system for 5-bit encoding of complete arabic-farsi languages - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method and apparatus for coding, transmitting, receiving, and displaying remotely or locally, all Arabic-Farsi characters or letters, basic arithmetic signs, numerals, punctuation marks and diacritical marks, as well as teleprinter operation commands in 5-bit standard Baudot codes. An Arabic-Farsi teleprinter similar in operation to the English teleprinter and compatible with the International exchange systems is provided without eliminating any letter forms. The teleprinter operation (the ability to compress the data into 5-bit characters) is based upon two basic criteria of the Arabic-Farsi languages, namely: 1) the form (start, middle, end or independent) of a character can be known if the preceding character and the following characters are known; and (2) there are six characters that are identical except for the presence or absence of a dot. The digital logic circuits make use of the above criteria to permit the encoding and thus the transmitting and receiving of complete Arabic-Farsi alphabets. A particular grouping of characters with level coder for each grouping, as well as a keyboard arrangement and control circuits for more versatile use of input/output devices are also disclosed.

Description

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B~C~GRO~ND OF THE INVENTIGN

Field of Invention This invention relates to a method and devices to be used in Arabic-Farsi teleprinters, typewriters, typesetting control, compu-ter input/ou-tput terminals, and displays. In addition the devices and method-may be applied to similar terminals which may combine Arabic with other languages.

State of the Prior Art Arabic scripts used for languages such as Arabic, Persian and Urdu (Arabic-Farsi languages) generally ,~
contain many more characters and character forms than are found in Roman script used for English, French, etc. Acco~dingly, coding techniques developed for transmitting, receiving, typesetting, and the like in connection with languages based upon Roman scripts may not be directly applicable ~or use in encoding and decoding of languages employing Arabic scripts.
A prime example of a codin~ technique that is used for transmission of the English language is the 5-bit Baudot code used in teleprinting throughout the world on the International exchan~e system. This 5-bit code can accommodate Roman script since only 26 letters or characters are involved and all 26 letters plus 10 numbers and various punctuations, symbols and functional keys can be accommodated by the Baudot code. On the contrary, it has been thought that the 5-bit Baudot code cannot accommodate -the 60 or more characters and character forms that might be required to provide for the transmission of good quality Axabic-Farsi languages by teleprintex. Accordingly, various compromises have been suggested as well as various coding techniques that require more than 5 bits and thus are not compatible with the existing In-ternational exchange requirements.
One solution offered by ~. S. Chaudhry in U.S.
Patent No. 3,998,310 does not provide all the character forms, does not take into consideration the require-ments for numerals, arithmetic signs, punctuation, and diacritical marks and expands coding requirements so as to be incompatible with e~isting teleprinter systems.
Chaudhry reduces the number of letters on a keyboard by dividing Arabic letters into two -Eorms, short form and full form, ignoring the other forms described hereinafter.
Charac-ters having both full and short forms are stored in short form when followed by another character and in full form when followed by space. Chaudhry also expands the coding re~uirements by using a 6-bit code with a seventh bit for "checking". Although it is suggested that other codes may be used, there is no disclosure of a system that provides Eor transmission and reception of complete Arabic-Farsi languages over standard teleprinter systems.
Hanson U.S. Patent No. 3,513,968 discloses a typesetting con-trol system in which 6-bit signals representing Arabic characters and space units are .

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stored ln a first shift register and successively decoded to classify the data into one of three classes for storage in a second shift register. A second decoder determines the form of the character from the character classification immedia-tely preceding and following the given character. The latter informa-tion, and the character form are used to address a memory to select a character in its desired form.
Hyder U.S. Patent No. 3,938,099 discloses a printing system in which Arabic characters are coded using 8 bits and 11 bits. An analyzer is provided to analyze the concatenation properties applicable to each character using Boolean equations based on knowledge of the variables of the preceding and follow-ing characters. Thls information from the analy~er combined with the character representation code and the composite code is then converted into a code suitable for driving output means.
Other approaches have been undertaken to reduce the number o~ required characters on machines such as teleprinters by omitting some Arablc character forms and deleting the arithmetic signs and punctuation marks so that the remaining number of characters and operations can be coded in the standard 5 bit binary Baudot coding. Another approach has been -to use the English (i.e., Latin or Roman) alphabet to transmit Arabic on English teleprinters.
None of the above approaches solves the problem of transmitting good quality Arabic plus the numerals, arithmetic signs, etc., over the International exchange ne-tworks which use Telex and Gentex Exchange systems and utilize s-tandardized 5-bit binary Baudot coding.
The elimination of characters greatly diminishes the quality of the Arabic language transmission and much of the expression may be lost or at leas-t may be difficult to read.
To achieve desired quality levels by past approaches has required many more than 5 binary bits for encoding the Arabic charac-ters. As a result, considerably more computer storage is required when Arabic script rather than Roman script languages are used in conjunction with computer sys-tems. Furthermore, the -transmission energy requirement of a given message is reduced as the number of bits per character is reduced so such xeduction i-s very desirable.

.1)61 BRIEF SUM~ARY AND OBJECTS OF THE INVENTION

It is accordingly an object of the present invention to provide a novel me-thod and system that overcomes the foregoing problems of the prior art.
It is another object of the present invention to provide a novel method and system for high quality reproduction of languages that use ~rabic characters wherein digital encoding and decoding is employed and each character is represented by and may be transmitted using no more than 5 binary bits.
It is yet another object of the present invention to provide a novel method and system for teleprinting Arabic-Farsi languages using existing International exchange networks includiny Telex a:nd Gentex Exchange systems wit~h a minimum of additional equipment and no ~.
change in the code now employed.
Still a further object of the invention is to provide a novel method and system for encoding and decoding the Arabic-Farsi lanyuages for transmission or storage wherein the input device may be used for -diverse purposes and is not tied to a sole function -such as that of teleprinting.
Yet a further objec-t of the present invention is to provide a method and system for telecommunication wherein messages may be transmitted and received on different languages employing different character forms.
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The apparatus and the method according -to this invention enable the user to transmit and receive up to four forms per letter of the Arabic-Farsi languages plus -the numerals 0-9, various tel.eprinter commands, the basic arithmetical signs, and a selected number of punctuation and diacritical marks. The transmitted and received code uses the standardized 5-bit binary Baudot coding. Hence the International Telex, and Gentex networks may be used to transmit complete Arabic-Farsi texts without compromising the quality of the language. Savings are obtained in the required number of code words and bits for the message and in computer storage requirements for the Arabic~Farsi texts.
In accordance with one embodiment of the inven~
tion, various characteristics of Arabic-Farsi languages are used to~provide for the complete reproduction of all Arabic characters as well as required numerals, punctuation marks, etc., required for complete tele-printing of Arabic-Farsi languages using standard ;~
5-bit coding. The language characteristics used include:

1. Although there may be more than 60 characters and character forms (or variations) in the Arabic-Farsi languages, there are 28 basic letters or characters in the Arabic-Farsi languages, some of these characters take different forms depending on the character preceding it and the character following it and the used calli-graphy style. Hence only one code word for each Arabic character is required to be transmitted if a logic is implemented at the receiver printer or display to select the required form and command the printer or output display, or device accordingly.

2. Certain Arabic letters are otherwise identical with the exception of a dot above each letter in a first group. Hence each letter in the first group can be recognized if a code is received for the dot followed by a code for the corresponding letter. Thus the required code words can further be reduced by five words.

3~ Arabic letters, numerals, punctuation marks, arithmetical signs, diacritical marks including the dot above selected letters, and teleprinter operational commands can be classified into th~e following types:

Type A; Those characters that join to the following character in a given word and join to the preceding character.
Type s: Those characters that do not join to the following letter in a given word but join the preceding character.
Type C: Those characters that do not join to the preceding or to the following characters. These include nu~erals, arithmetical signs, and punctuation marks.

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Type ~: Those characters that do not cause the carriage or printing cylinder, or display to move to the next space such as diacrltical marks, and the upper case and lower case signals. .~

~ype 0: Those teleprinter operational ~:
commands such as "Who are you?", Here is, sell, Carriage return, and Line feed.

4. The diacritical marks fall above or below the corres- ' ponding le-tter the same as the dot above the letters.
When diacritical marks are printed they do not cause the carriage feed or the printiny cylinder, or ball or C~T display to advance to the next space and do not affect the choice of the letter form. Alsor the trans-rnission of the teleprinter commands such as change from upper to lower case and.vice-versa are not printed and do not cause carriage feed, or display space movement.
Accordlng to another embodiment of the invention, the characteristics of the Arabic-Farsi languages , specified in paragraphs 1, 3 and fi above are used to decrease the total numbexs of code words required to encoda a complete ~rabic-Farsi language. Moreover, additional code words are made available for encoding by sacrificing at least three code words as level indicators. These level indicator code words, when present in a sequence of character code words, specify .;
that the immediately following code words in a sequence ::
are of a predetermined group of characters. In this manner, a 5-bit code can be used to encode up to 93 charac-ters (96 minus the 3 level code words), and a complete Arabic-Farsi lanyuaye as well as o-ther charac-ters such as Telex control characters, numerals, etc., can be encoded.
In addition to the foreyoing, one aspect of the invention involves a technique for reducing the number of keys on an Arabic-Farsi typewriter or teletypewriter keyboard by providing only one form of a multiple-form character on the keyboard. An Arabic adapter in accordance with the foregoin~ principles is employed to determine the true form of the character and, despite the fewer number of keys, the complete Arabic-Farsi language can be produced. It will be appreciatec1 that this arrange-ment greatly simplifies the keyboard and simplifies the task of the machine operator thereby facilitating both the operation of the machine and the training required.
Another aspect of the invention involves the provision of con-txols that permit an Arabic-Farsi keyboard controlled prin-ting device to be used both as a teletypewriter and a typewriter. ~lso provision is made for using both Latin and Arablc-Farsi devices with peripheral units such as a tape punch.
Using the above characteristics, this invention provides apparatus and a method to code the complete Arabic alphabet, the numerals, the basic arithmetic signs, and the selected punctuations, and diacritical marks, plus the teleprinter operational commands in

5-bit binary Baudot codes. Apparatus is provided to interface with the printer, or display so that all the required Arabic letter Eorms can be indicated and printed or displayed accordinyly.
The ~oregoiny objects and advantages of the invention will become apparent to one skilled in the art to which the invention pertains from the following detailed description when read in conjunction with the appended drawings.

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BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a functional hlock diagram of a tele-printer sys-tem operable in accordance with the present invention to transmit and receive Arabic-Farsi languages using standard 5 bit codes;

Figure 2 is a functional block diagram illustrating the Arabic adap-ter circuit of Figure 1 in greater detail;

Figure 3 is a functional block diagram illustra-ting in greater de-tail a coder that automa-tically causes -the generation o~ a dot code and a charac-ter code when certain characters are commanded by a user;

Figure ~ is a pictorial representation of one fo:rm of teleprin-ter keyboard that may be utilized in conjunc-tion with -the present invention for transmission and reception of Arabic; and Figure 5 is a pictorial representation of a variation of the keyboard of Figure 4 with the English (~oman) characters also appearing on the keys as they are shown . in Table III herein.

Figure 6 is a table indicating the groups of classification of the Arabic-Farsi characters in the teleprinter or telex operations in order to illustrate one form of the character type classification according to the Figure 1 embodiment of the invention;

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Figure 7 is a table summa.rizing the rules for determining the letter form according to the present invention;

Figure 8 is a table illustrating an example of ;~
saudot coding of Arabic Farsi characters in accordance with one embodiment of the invention;

Figures 9a and 9b indicate the two groups o:E
Arabic-Farsi characters that are similar except for a :
dot above each character in one group that does not ~ ;
appear in the other; ~ -..~' Figure 10 is a table illustrating another example of Baudot coding oE Arabic-Farsi characters in accordance with the present invention wherein three level codes ~
are used and the characters are placed into three ;.
groups for coding;

Figure ll is a functional block diagram of an - :
embodiment of the present inven-tion compatible with up ;,'.
to three groups of characters;

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~ Figure 12 is a plan view schematically illustrating an abbreviated keyboard input device in accordance with :
the present invention; and ~ `.

Figure 13 is a functional block diagram of an embodiment of an Arabic-Farsi printing system employing -13~

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an abbreviated keyboard input device as shown in Figure 12.

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DETAILED DESCRIPTION OF ~ PREFERRED EMBODIMENT

Arabic letters or characters are baslcally 28 in number but some le-tters may have as many as four diEferent forms depending upon their position in relation to other characters. As indicated in Figure 8, there are charac-ters which may take four forms, while others may take three forms, others two forms, and others only one form.
The form of the character is decided upon in accordance with the logic and classification se-t forth in Figures 6 and 7.
In accordance with the preferred embodiment of the invention, Arabic letters, numerals, arithmetic signs, punctuations, diacri-tic marks (including the dot above selec-ted letters), and the teleprinter operational commands a~e classified into the five types of teleprinter characters Ar B~ C~ D, and O previously defined and in Figure 6.
The Arabic-Farsi letter Eorms may be one of four possibilities: the start form, the middle form, the end form, and the independent form. The form of a ~ -letter is logically determined in the preferred embodi-ment according to the rules in Figure 7 where the (+) sign means "or."
Figure l illustrates a teleprinter system in accordance with the present invention which utilizes the foregoing criteria to transmit and receive Arabic-Farsi languages using standard 5-bit coding tachniques.

Referring to Figure l, a keyboard ll is connected by a .. ~ :

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line 12 to a conventional 5-bit Baudot coder 13. The keyboard 11 may be a standard English keyboard arranged with the Arabic letters, the numerals, the arithmetic signs, and the selected punctuations and diacritical marks plus the teleprinter commands as shown in Figure 8 hereinafter by way o example. The coder 13 codes the characters into 5-bit binary Baudot codes. Figure 8 also provides an example oE a Baudot 5-bit binary coding arrangements for the keyboard characters.
The 5-bi-t coder 13 is connected by a line 14 to a conventional memory or tape punch 15 which is controlled by a suitable memory or tape punch control 16 by way of line 129. The 5-bit coder 13 is also connected to a conventional modem 111 by a line 13 and the modem 111 is connected to a conventional transmitter 117 and to a conventiQnal receiver 113. The transmitter and receiver are controlled by a conventional call control circui-t 119 by a line 116 as illustrated.
The modem 111 and -the memory or tape punch 15 are interconnec-ted as schematically indicated by the lines 126 and 128. The memory or tape punch 15, the 5-bit coder 13 and the modem 111 are also connected as is schematically illustrated by the respective lines 17, 18 and 110 to a switch 125. The switch 125 selectively connects the three units 13, 15, and 111 either to a ~-conventional English or other language printing or `
display unit 124 or to an Arabic adapter 120 hereinafter described in greater detail. The Arabic adapter 120 is connected to an Arabic printing or display unit 122 ~Lf~

such as a conventional CRT display or a conventional Arabic typewriter.
The keyboard 11, the 5-bit coder 13, the memory or tape punch 15, the memory or tape punch control 16, the modem 111, the receiver 113, the transmitter 117 and the call control 119, as well as the English or other language printing or display unit 124 together make up a standard teleprinter unit of the type commercially available ~or English language or other Roman character based language transmission. The one difference in this system is that the keyboard 11 is provided with Arabic letters, numerals, arithmetic signs, selected punctuations, diacritical marks and in one embodiment third level coding, as well as the teleprinter commands shown, for example, in Figure 8. Moreover, the switch 125 would ordinarily be unnecessary :in a one language system.
The teleprinter of Figure 1 may operate in a transmit or receive mode, or in a purely local mode in which mode data is neither transmitted nor received. In local mode, the transmitter 117 is disabled so that data entered by way of the keyboard 11 is not transmitted. The data is, however, coded by the 5-bit coder 13 to form 5-bit . ~.
Baudot codes. These 5-bit codes are supplied either to the printing or display unit 124 or the Arabic adapter 120 depending upon the position of the switch 125.
Assuming that the system is set up for Arabic operation and the user is using the Arabic characters on the keyboard 11, the switch 125 will be in the position z~

illustrated. The keys depressed on the keyboard 11 result in a 5-bit code for each depressed key and this 5-bit code is supplied to the Arabic adapter 120. The Arabic adapter translates -the 5-bit codes into 8-bit codes by addinc3 2 bits to indicate the proper form oE
the character and 1 bit to indicate whether the character is upper or lower case. The additional 2 bits indicating the form of the character are arrived at by utili2ing the previously described characteristics of the Arabic-Farsi languages.
If the teleprinter is operating in the receive mode with the switch in the illustrated position, the data received on input lead 114 by the receiver 113 is supplied by the modem 111 to the memory or tape punch 15 and the Arabic adapter 120. Depending upon the state of the memory or tape punch control 16 the incoming data may be stored by the memory or tape punch 15 in a conventional manner. The data supplied to the Arabic adapter 120 is translated in-to the 8-bit signal previously described and causes the printlng or display unit 122 to reproduce the proper Arabic characters.
If the teleprinter of Figure 1 is operating in the transmit mode with the switch 125 in the illustrated Arabic position, the transmitter 117 is enabled and the 5-bit codes from the coder 13 are supplied both to the Arabic adapter and through the modem 111 to the transmitter 117. The modem may alternatively receive 5-bit codes from the memory or tape punch 15 by a line 128 as in typical conventional teleprinter systems. Figure 8 provides an example of 5-bit binary saudot coding oE
Arabic as compared to English character coding on a standard teleprinter ]~eyboard. The codes are 32 in number but many more than 32 characters can be encoded because the ~eys can be operated either in upper or lower case. Also, the characters listed in slots 33~38 do not have separate codes but are made up of a composite of the dot code (00000) followed by the corresponding character code. It will be appreciated from Figure 8 that all of the ~rabic characters and character forms are provided on the keyboard in addition to the numerals, the arithmetic signs, the selected punctuations and diacritical marks, and the teleprinter commands of a standard teleprinter. The code for the characters listed as 33-3~ may thus be formed by first depressing the key (and thus generating the code~ Eor the dot and then depressing the key for the character or by depressing only one key and automatically generating both codes as is described hereinafter. ;;
It can be seen from Figure 8 -that those characters having more than one form are provided only one key position on the keyboard and one corresponding 5-bit code. Thus, one 5-bit code represents a character that may have up to four forms with nothing in the 5-bit code itself to indicate the form of the characters. The receiving end of the system (i.e., a remote receiver or a local printer) must therefore determine the form of the character from the foregoing criteria.

The Arabic character in the lower case keyboard position labelled number 1 ln Figure 8, for example, corresponds to the English Q (see Figure 5 for example).
The Arabic character in the number 1 position in the table of Figure 8 and the English Q are therefore encoded with the same code, i.e., 10111. Accordingly, if the Arabic character in the number one position in the table of Figure 8 is depressed on the keyboard of Figures 1 and 5 the coder 13 will produce the 10111 code. If the switch 125 is in the illustrated position, one of the two forms of the Arabic--Farsi character in the number :
one position in Figure ~ will be reproduced depending on the position of the character relative to other characters. Similarly, if the switch 125 is in the position connecting the coder to the printing or display unit 12~, the letter Q will be printed. It will there-fore be appreciated that the Arabic adapter 120 makes the decision based upon the previously described criteria as to what Arabic character form will be printed despite the fact -that the 5-bit code does not directly :
carry information as to the forms of the character.
One embodiment of the Arabic adaptex 120 of Figure 1 i5 illustrated in greater detail in Figure 2. Referring now to Fi~ure 2, it will be seen that the Arabic adapter provides for the utilization of the standard 5-bit saudot code in the transmission and reception of Arabic-Farsi languages and provides the ability to print all Arabic characters in their exact forms at the receiving end of the transmission system. It will also be _ _ _ _ . _ _ .. . . . . . .. .. _ _ . .. , . . , , ~, ~Z~6~

appreciated that the technique used to accomplish this result in the circuit of Figure 2 includes (A) identifi-cation of a sequence of characters as upper or lower case, (s) identification of each character by type including whether -this character is printed with or without carria~e feed and whether carriage feed occurs without printing, and (C) utilization of the information of (A) and (B) above in conjunction with delay so that a form for each character is identified at the time of pri.nting. It will be seen that because of the delay the printed character is, in general, one character behind the last charac-ter received.
Referring now to Figure 2, the ~rabic adapter includes two position selec-tor switches 25 and 28 which select coded character information and character indicator info:rmation (a strobe signal IND that acts as a timing signal for the received information), respec-tively, from eithe.r a local keyboard or mernory, or from a transmission system. For example, in one position of the switches 25 and 28, a 5-bit saudot code and a valid character indicator signal (the strobe) will be accepted fron~ the transmission system modem 111 of Figure 1. In the other position of the switches 25 and 28, the character and character indicator code will be accepted from the keyboard coder 13 of Figure 1.
The selected character is supplied as a 5-bit signal along line 26 to a conventional 5-bit parallel in/parallel out shift register 210. The output signai from the register 210 is supplied to a second identical . . . ~

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shift register 220, to an upper and lower case xecognizing circuit 218 and to the address inpu-t terminal of a read only memory (ROM) 231.
The valid character indicator signal selected by the switch 28 is supplied along line 29 to a conventional dela~ circuit 213 such as a flip flop and to one input terminal of a gate 216. The output signal from the delay circuit 213 is applied over line 212 to the shift input terminal of the xegister 210 and to a second conventional delay circuit 214. The signal from the second delay circuit 214 is supplied to a third conventional delay circuit 222 and to one input terminal of a conventional three input terminal logic gate 235. The output signal from the delay circuit 222 is supplied to the clock input terminal of a register 227 and to one input terminal of a loyic gate 247.
The change output signal from the upper and lower :
case recognizer 218 indicating that a change from upper to lower case or vice-versa has occurred is supplied to one input terminal of the ga-te 235, to an inverting (negative logic) input terminal of the gate 216, and to one input terminal of each of three conventional logic gates 243, 245, and 247 (e.g., AND gates). The output signal *rom the logic gate 216 is supplied along line 217 to the clock or shift input terminal of the register 220. The output signals from the logic gates 243, 245, and 247 are supplied to the printer 122 of Figure 1 as the respective indicator (IND), carriage feed (CARRFEED) and print (PRINT) signals.

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' ,he read only memory 22~ receives an 8-bit address signal ~the delayed character plus the upper/lower case STATE plus a 2-bit signal MODE specifying the character form) and supplied an ~-bit charaçter code to a conven-tional 8-bit register 227. The output signal C~AR
from the register 227 is -the code identifying which character form is to be printed.
The read only memory 231 receives 6 bits of informa-tion, including the last received 5-bit character code and the current upper/lower case STATE, and provides four bits of information specifying the type of character received (TYPE), whether or not the carriage should be moved (C~RRIAGi~) and whether or not -the character should be printed ( PRINT)o The T~PE signal is a 2-bit code supplied to both a register 236 and a logic circuit 241. The type of charac-te:r may be type A, B, C, or O
as was previously described (the type D being excluded since it is a non-carriage character). The CARRIAGE
signal is a l-bit signal specifying whether or not a movement of the carriage is specified by the current character. The PRINT signal is a l-bit signal specifying whether or not -the character is to be printed (e.g., type O characters will not be printed~
The TYPE signal is applied over line 232 to the data input terminals of two stages of a conventional four bit parallel in/parallel out shift register 236.
The output signals from the first two stages are applied via line 238 to the input terminals of the other two stages of the register 236, and the output signals from .. . . _ .... . . . . i , .. .. .. _ _ . , ~ , _ these latter two stages are applied as the PRECEDE signal to a conventional logic circuit 241. The TYPE signal is supplied to two other input terminals of the logic circuit ~41 as the FOLLOW signal. The logic circuit 241 may be any conventional logic circuit ~e.g., a plurality of AND, OR, NAND, or NOR gates) connected in a conven-tional manner to solve the eguations of Table II. The resulting Mode signal thereby indicates by 2 bits one of the four possible forms previously discussed.
In operation, switches 25 and 28 enable selection of the 5-bit Baudot charac-ters plus a valid character indicator from either a local keyboard or from a trans-mission system. The transmission system will be of the standard 5-bit Baudot type.
The character indicator pulse is conventionally provided in a teleprinter system to indlcate the presence ~ ;
oE a character. This pulse :is delayed by the respective delay circuits 213, 214, and 222 to provide ~or a controlled order of sequence of events described below.
The upper~lower case recognizer 218 examines the last received character in register 210 and provides two output signals. The current state output signal STATE indicates that all characters are either upper or lower case depending upon the ~inary state so indicated and until the state is unchanged. For example, a binary ONE on line 229 might indicate upper case while a ZERO
might indicate lower case. The CHANGE signal on 219 indicates a state change when the last received character was an upper or lower case indicator character~ If the ~10~

last received character was an upper or lower case indicator (i.e., the character indicating the upper or lower case key as shown in Figure ~ has been depressed) then the only activity on the next character is the change of the state 229 and loading of register 210, while the CHANGE signal on lead 219 inhibits gate 216 and prohibits loadiny of register 220.
If -the last received character is not an upper or lower case indicator, then the next received character indicator pulse on lead 29 is passed by gate 216 and causes the previous character in regis-ter 210 to be transferred to register 220.
Next, aftex the delay Tl the latest character received over line 26 is stored in register 210 in response to the delayed pulse from circuit 213. This latest 5-bit character along with the l-bit STATF, signal produces a 6-bit address for the read only memory (ROM) 231. This ROM stores a 4-bit word for each address. Two bits identify the form as O, A, B, or C as indicated in Figure 7, one bit indicates if carriage feed is associated with this character and one bit indicates i~ printing is associated with the character. For example, a space does not involve printing while adding a dot or diacritical mark to a character involves printing but does not involve -carriage feed.
Next a~ter additional delay T2, the TYPE data in register 236 is advanced by the signal from logic gate 235. If the character in register 210 is an upper or lower case indicator, or if carriage feed is not ~L~2~

associated with this character including -the U/L case state as indicated by the CARRIAGE signal on line 233, then the data in register 236 is not advanced. When the data is advanced then the 2 binary bits of -the TYPE
signal are stored in register 236 and appear on leads 238 while the previous data on leads 238 is simultaneously advanced to appear on leads 240 of register 236. The resulting 4 bits applied Erom the register 236 to loyic element 241 produces a ~ODE output signal. The MODE output identifies the character form as being either of the start, middle, end or independent form as indicated in Figure 7. The 5-bit character code from register 220 -together with the character form signal MODE and the upper/lower case state signal thus form an address that selects the indicator for the proper character form from the appropriate Memory location of the ROM 224 for printing.
The final operations are the loading of register 227 after an additional delay T3 and an outputting of a character indicator to the printer via lead 248. If the last received character was an upper or lower case indicator then the character indicator signal IND, carriage feed signal CARRFEED, and print commands PRINT
to the printer are all inhibited. Depending upon the type of prin-ter being used, the independent carriage feed and print commands may not be necessary since this information is also inherently contained in the 8-bit character 228 being fed to the printer.

The final selection of up to an 8-bit (some systems may require only 7 bits) character data for the printer is accomplished in ROM 224. The 8-bit address -to this ~OM is composed of 5 bits 221 of-the originally received saudot character, one on bit 229 indicating upper or lower case, and 2-bits 242 indicating mode as was previously described.
As was previously men-tioned, there are six Arabic letters or characters that are formed identically to six other but quite different charac-ters except that the latter six include a dot over the character. ~ith the keyboard discussed in connection with Figure 8 it was suggested that -these letters with dots could be encoded for subseguent decodiny by providing a "dot" key on the keyboard, which key could be depressed before depressing any of the.six "non-dotted" characters already on the keyboard to -transform these to the "dot" characters. As an alternative, the character with the dot itself can be placed on the keyboard as shown in Figure 4 and a circuit such as that shown in Figure 3 can be used to automatically generate the dot code plus the code of the corresponding characters whenever these keyboard characters are depressed. It will, of course, be appreciated that this requires no additional code words but merely simplifies the operation of the keyboard.
Figure 3 illustrates a circuit that causes the transmission of a dot code ~00000) followed by the code of the corresponding letter when any of the letters with the dot above is selected. For example if the third o~

character from the left in Figure 9a is selected, two character codes will be transmitted; namely (00000) for the dot followed by (10101) Eor the character that corresponds to the dotted character (the third character from the left in Figure 9a).
The six input characters, the first of which is iden~ified by the numeral 301, are the six Arabic letters without the dot and they are processed ln the S-bit keyboard coder 305 as previously descri~ed. The same six letter forms (e~cept for having the dot) are identified by the number 302. Through six OR gates 303 each letter activation on -the keyboard of one of the six letters with or without the dot en-ters the coder 305 identically~ In addition, a six input terminal OR gate 304 provides an output signal on lead 31~ in response to the entry of one of the six "dotted" letters.
The character indicator pulse on line 318 from the coder 305 is combined through AND gates 3:L0 and 311 with the signal from the OR gate 304 and its inverted form, respectively. The signals ~rom -the AND gates 310 and 311 and the signal from the coder 305 are then used ~ith a conventional delay circui-t 312, OR gate 308, AND
gate 306, and OR gate 313 to produce the following responses and outputs.
If a key 301 for the letter without the dot is activated then the AND gate 306 is enabled to cause the 5-bit character to appear at the output terminal 307 during the occurrence of a single character indicator on lead 317.

If a key 302 for a letter with a dot is activated, then two sequential charaeter indieator pulses oeeur on ou-tput lead 317 separated by the -time delay 312 which will be in the order of 10 to 30 milliseeonds to enable separation but to prevent operator ac-tivation of another key before the double eharaeter out is completed. During the first character indicator pulse CHAR IND, the AND
gate 306 is disabled so that -the outpu-t on lead 307 is the all ZERO code for the dot. During the second eharacter indicator pulse, the OR gate 308 is enabled so that the code for the charaeter without the dot 301 whieh is on lead 306 out of the eoder now appears at -the output 307.
In the Flyure 1 embodiment of the invention using the eharae-ter grouping and eoding oE Figure 8, a dot eode is prQvided to aeeount for the differenee between the eharacters o-f Figures 9a and 9b. As is illustrated in the table of Figure 10, the eharaeters are elassified into three yroups and a level code is provided for eaeh group. In -this manner it will be appreeiated that as many as 93 character and con-trol eodes are available.
Aeeordingly, all the information shown in Figure 10, as well as additional information if necessary or desirable, can be eneoded for transmission or storage.
It ean be seen from Figure 10 that two of the level codes are the lower and upper case codes 11111 and 11011, respeetively. The all zeros code (00000) may be used as the third level code.

With such a three-level system, the circuit o~
Figures 1 and 2 may be utilized with a slight modifica-tion to the upper/lower case recognizer circuit 218 and the read only memories so that the third level code can be recognized and utilized to address the appropriate characters in memory, as was discussed previously. Of course, such functions as were previously mentioned can be implemented using standard microprocessor and memory chips (integrated circuits) in order to provide added flexibility.
Alternatively, a circuit such as that illustrated in Figure 11 may be utilized. Referring to Figure 11, a keyboard 44 such as that illustrated in Figure 4 (or a standard Arabic typewriter keyboard with additional telex operation keys) supplies an ASCII coded character signal CHAR to an input memory 402, and a strobe signal CHAR IND is supplied to an input logic circuit 404.
The CHAR signal from the ~eyboard is an 8-bit ASCII
signal when using commercially available equipment, so the input memory 402 utilizes this code and a 2-bit code LVL from the input logic circuit 404 to address appropriate 5-bit Baudot codes CHA~' in memory. Also, there is a 3-bit identification code ID stored with the 5-bit code in memory and this 3-bit code is supplied to the input logic circuit 404.
The CHAR' signal is supplied to conventional "first-in, first-out" (FIFO) circuit 406, which is controlled by IN and O~T signals from the logic circuit 404. The FIFO conventionally "smooths" the transmission rate of ....--the CHAR' signal so that this rate is relatively uniform and does not exceed the capacity of a telex or a printer (e.g., does not exceed 75 bauds).
The 5-bit character signal C~AR' is supplied from the FIFO to a conven-tional "universal asynchronous receiver-transmitter" ~UART) 408 which in turn supplies this signal for transmission as the TS signal to con-ventional interface circuits (STUNT CIRCUITS) ~10 that control transmission and reception of signals at acceptable levels and n appropriate forms. Control slgnals for the STUNT circuits 410 are supplied from a signal control logic circuit 412 which receives control signals LOCAL
and OFF-LINE from the keyboard or other control signal source~ Thus, with the system in telex mode (not in LOCAL and not OFF-LINE) the input information from the keyboard 40.0 is directed out of the STUNT circuits to the TTY and to the UART for simultaneous transmission and printing. With the system in LOCAL mode, the TS
signal will be routed to the printer (as the RS signal) by the STUNT circuits and also to the routing switch (not shown)~ The routing switch may route the information signals to a paper punch or other type of memory so that the keyboard data may be recorded as it is printed. Also, the system may be placed OFF-LINE so that any incoming ;-data received by the STUNT circuits will be applied to the routing switch for recording and later printing.
With continued reference to Figure 11, the RS signal from the UART is applied to a printing control circuit similar to the input circuit in the sense that the level ~z~

code is recoynized to assist in recognizing the received character, the form of the character is determined and an appropriate character is selected by meMory addressing as was previously discussed. In this connection, the RS sigllal is applied to a register 414 (Register 1), the output signal of which is applied to a register 414, whose output goes to a register 416 and a register ~18.
The output signals from registers 416 and 418 are supplied to an output memory 420 which supplies a PRINT
signal (the ASCII coded or otherwise compatible character code) to a sui-table printing mechanism such as the tele-typewriter solenoid drivers that drive the individual character printing devices. The PRINT signal is also :
supplied to an output logic circuit 422 that provides the print strobe signal PRINT STRB to the teletypewriter or other output device. The output logic circuit also provides a 2-bit level indicating signal to the Register (414) and control signals that control the loading o-f the registers 414-418.
In operation, the 7-bit character signal CHAR from the keyboard and the LVL signal from -the input logic circuit 404 select the proper 5-bit 13audot code from the memory 402 for application to the FIFO. The selected code is strobed into the FIFO by the logic signal I2~.
Also, the logic circuit 404 determines the group in which the character belongs and causes the appropriate level code to be accessed in the memory and placed into the sequence of character codes.

L

The input logic circuit also determines from the ID
signal if the accessed code is tha-t of a diacritical mark.
I-f it is, it does not have any par-ticular form associated therewith ~e.g., start, middle, end, independent) and, :
when placed into a sequence of characters it is printed over the imrnediately preceding character. Thus if a sequence of characters Cl, C2, C3, C4 is transmitted with a diacritical mark DM between C~ and C3 (i.e., the sequence Cl, C2, DM, C3, C4) the DM must be printed before the C3 is received, DM is printed when Ll is received and C3 is printed when C4 is received. The printer may therefore be held up occasionally but neve.r has to print at a faster than normal speed. Of course, the FIFO
functions as a smoothing buffer during the insertion of the level codes and during any non-uniform insertion of characters.so that a uniform transmi.ssion rate is achieved.
When receiving characters for printing, Register 1 contains the last received character code. The next received character causes the contents of Register 1 to be transferred to Register 2 (or to Register 3 if Register 1 contains a diacritical mark) and this next received character is strobed into Register 1. The output logic 42~ determines the form of the character and supplies form ID signals FID to the output memory 420 along with the S-bit character code. The form of the characters will of course depend upon the 5-bit code, the position of the character in a word and the level code preceding the character (first, second, or third le~el). Whether or not the character is a diacritical mark determines .

the printing procedure since diacritical marks do no-t cause a carriage feed. In this connection, a diacritical mark will be stored in Register 3 and a timing sequence will start so -that the time order of printing previously discussed will occur (i.e., Cl, C2, DM, C3, Ll, C4).
In accordance with -the present invention, the Arabic ~ ;
adapters of Figures 2 or 11 may be utilized to simplify the keyboard of an Arabic typewriter or other such printing machine to thereby increase the operator's speed and also simplify training. The manner in which this may be accomplished is illustrated in Figures 12 and 13.
Referring now to Figures 12 and 13, a simplified Arabic-Farsi keyboard 450 having only one form of each letter is connected to the Arabic adapter 120 such as that illustrated in Figure 2. In this connection, the signals indicated a~ the inpu~ and output terminals of the adapter 120 are the same as those shown in Figure 2.
The ou-tput signals ~rom the adapter 120 are supplied to a suitable conventional printer or other suitable output device 452.
The line 211 from -the register 210 of the Arabic adapter (as shown in Figure 2) supplies the last entered character code to a light emitting diode (LED) display 452 for display of the last entered character. This LED display may be positioned in any suitable location readily visible to the machine operator.
In operation, the machine operator is provided with a keyboard 450 with keys for only one form of the Arabic-Farsi characters. Accordingly, it can be seen that each charac-ter can be typed without the necessity of shifting from one character level to another (e.g., as with upper to lower case shifting that is required when one key is used for two characters). When a word is typed, the code for each charac-ter key depressed by the operator is generated in a conventional manner and the Arabic adapter 120 determines the form of the character by its position in the sequence of characters as was previously described.
The character that is typed or printed is thus the proper form of the character despite the fact that the operator always inputs only the one form on the keyboard. In this regard, it should be noted that the output device is of the type discussed previously (e.g., a conventional complete Arabic-Farsi language typewriter output) and is capable of printing all forms of the charac-ters.
Since the Arabic adapter 120 provides an output character only after two successive characters have been entered by the keyboard, the LED display is provided to display the last entered character. This display may not be necessary for the trained operator but it may be helpful should interruptions in the typing occur. -~-It will be appreciated that this simplified form of keyboard greatly reduces the amount of shifting presently required on a standard ~rabic typewriter.
Whereas a good typist may be able to type 35 to 40 words ~ -per minute on a standard device, it is contemplated that speeds will almost double to a rate comparable to that on Latin machines using the device of Figures 12 and 13.

It will also be appreciated that a standard ~rabic keyboard with all forms of the ~rabic-Farsi characters can be used in the event that an operator previously trained on such a machine wishes to continue with its use.
This same system illus-trated in Figure 13 may still be used, however, and the shifts from upper to lower case or vice-versa need not be made or, if made, are ignored in encoding the characters.

.
The present lnvention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It should be under-stood, for example, that the present invention is readily usable for the storage and re-trieval of informa-tion as shown in Figure 1 merely by operating in local mode and recording or storing information in memory 15 as it is keyed in through the ~eyboard 11. When it is desired to use the information, it can be retrieved and applied through the Arabic adapter for display. The presently disclosed exemplary embodiment is therefore to be considered in all respects as illustrative and not res-trictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (27)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A teleprinter system for Arabic-Farsi languages comprising;
means for generating a succession of 5-bit codes each representing an Arabic character of the Arabic-Farsi language or one of a plurality of standard teleprinter characters including teleprinter numerals, punctuation, and command characters, without regard to the form of the Arabic characters;
means for inserting one of at least three 5-bit codes into the succession of 5-bit character codes to identify at least one subsequent character code as being in one of at least three predetermined groups of characters associated with the inserted one of the three 5-bit codes;
means for receiving and storing the 5-bit code for at least two successive characters;
means responsive to the stored 5-bit codes for classifying each received character as one of a plurality of predetermined character types;
means for generating a second code identifying each stored 5-bit code representing an Arabic character as one of four possible Arabic character forms in response to the classified type of the character immediately preceding and immediately following the first stored of the characters;
means for displaying in its proper form and position each Arabic character represented by a stored 5-bit code in response to said second code and the stored 5-bit code, including means for displaying successive characters in the same position in response to an indication from the classifying means that a character to be displayed is of a character type for which the display position is not to change.

2. The teleprinter system of claim 1 wherein said classifying means conprises means for specifying each received character as a character of the type that joins to the preceding or following character in a given word, a character of the type that does not join the following character in a given word but does join the preceding char-acter, a character of the type that does not join either the preceding or following character, a character of the type that does not cause the movement of the display to another space, or a character of the type that specifies a teleprinter operation command.

3. The teleprinter system of claim 1 wherein the six Arabic letters ( ) are coded as a 5-bit code specifying a dot followed by a 5-bit code specifying the corresponding one of the forms ( ).

4. The teleprinter system of claim 3 wherein said classifying means comprises means for specifying each received character as a character of the type that joins to the preceding or following character in a given word, a char-acter of the type that does not join the following character in a given word but does join the preceding character, a character of the type that does not join either the preceding or following characters, a character of the type that does not cause the movement of the display to another space, or a character of the type that specifics a teleprinter operation command.

5. The teleprinter system of claim 4 wherein said displaying means comprises means for generating an 8-bit code specifying the stored 5-bit code as one of a plurality of possible characters including all Arabic characters and forms thereof, standard teleprinter operation commands, punctuation, numerals and diacritical marks, wherein the possible characters and character forms number over one hundred.

6. The teleprinter system of claim 1 wherein said displaying means comprises means for gnerating an 8-bit code specifying the stored 5-bit code as one of a plurality of possible characters including all Arabic characters and forms thereof, standard teleprinter operation commands, punctuation, numerals and diacritical marks, wherein the possible characters and character forms number over one hundred.

7. An adapter for effecting the decoding of Arabic-Farsi languages that have been encoded as a succession of Arabic characters together with other characters including numerals, arithmetic signs, punctuation, operation commands and diacritical marks as a sequence of 5-bit digital character codes without regard to the form of the Arabic characters of the language comprising:
means for inserting one of at least three 5-bit codes into the sequence of 5-bit digital character codes to identify at least one subsequent character code as being in one of at least three predetermined groups of characters associated with the inserted one of the three 5-bit codes;
means for momentarily storing each 5-bit digital character code in a sequence that forms the Arabic-Farsi language;
means responsive to the stored 5-bit digital character code for classifying each character as one of a plurality of predetermined character types as a function of the 5-bit digital character code preceding and following the stored 5-bit digital character code in said sequence;
means responsive to said classifying means for generating a second digital code specifying the form of each Arabic character represented by the stored 5-bit digital character code; and, means for generating a third digital code of greater than 5-bits specifying the character represented by the stored 5-bit digital character code, including the form of said character specified by said second digital code, in response to said stored 5-bit digital character code, said second digital signal and said inserted one of the at least three 5-bit codes.

8. A method of teleprinting Arabic-Farsi languages comprising the steps of:
generating a succession of 5-bit character codes wherein each 5-bit character code represents an Arabic character of the language or one of a plurality of characters including punctuation, numerals, commands, and diacritical marks, the 5-bit code of each Arabic character representing the character without regard to its form;
inserting one of at least three 5-bit codes into the succession of 5-bit character codes to identify at least one subsequent character code as being in one of at least three predetermined groups of characters associated with the inserted one of the at least three character codes;
transmitting the succession of 5-bit character codes and the inserted 5-bit codes to a remote location;
receiving the succession of 5-bit character and inserted codes at the remote location and momentarily storing each received 5-bit code;
classifying the character represented by the stored 5-bit code as one of a plurality of possible character types;
for each 5-bit code representing an Arabic character, generating a form code specifying the form of the Arabic character represented by the 5-bit code as a function of the type of character immediately preceding and following the stored 5-bit character code; and displaying the received succession of 5-bit codes as Arabic characters in their proper forms and positions and as other characters specified by the 5-bit codes in response to both the 5-bit codes and the form codes, successive characters being displayed in the same position in response to an indication that a received character is of a predeter-mined type for which the display position is not to change.

9. A method of storing and retrieving data in an Arabic-Farsi language wherein the data are represented by a sequence of 5-bit digital words with each word representing a character of the data, the method comprising the steps of:
assigning each character of the data to one of at least three predetermined groups and inserting into the sequence of 5-bit digital words one of at least three 5-bit codes identifying at least one subsequent 5-bit word as being in one of the at least three predetermined groups;
storing the data as a sequence of 5-bit digital words each representing a character of the data, including Arabic characters, without regard to the form of the Arabic characters;
retrieving the 5-bit digital words in sequence from storage and determining the form of each Arabic character represented by a 5-bit word as a function of the identify of the Arabic character and of the 5-bit word preceding and following the Arabic character; and displaying the data including the Arabic characters in their proper forms and positions with some positions being the same for two successive characters in response to the retrieved 5-bit digital words and the determined form of the Arabic character.

10. An electronic typewriting system for Arabic-Farsi languages comprising:
a. a keyboard having a plurality of keys each corresponding to at least one of a single form of an Arabic character of the Arabic-Farsi language, a numeral, punctuation and command character and means for generating a succession of multi-bit character codes in response to actuation of the keys, wherein each character code represents one of an Arabic character of the Arabic-Farsi language, numerals, punctuation and command character and the character code for each Arabic character is independent of the form thereof;
b. an Arabic adapter for converting the form independent character codes into the proper language form for display comprising i. means dividing the characters into one of at least three groups and for inserting one of at least three multi-bit level codes into the succession of character codes to identify at least one associated character code as representing characters of one of the three groups of characters;
ii. means for receiving and storing the codes for at least two successive characters;
iii. means responsive to the stored codes for classifying each received character as one of a plurality of predetermined character types; and iv. means for generating a form code for each received Arabic character identifying same as one of four Arabic character forms in response to the classification of the character immediately preceding and immediately following the Arabic character under consideration; and c. display means responsive to the received codes and the form code for each of a succession of characters for displaying the last entered character in a first display without regard to form and for displaying each Arabic character in its proper form in successive positions in a second display including means for displaying the successive characters in the same position in response to an indication from the means for classifying that a received character is of a predetermined type for which the display position is not to change.

11. The system of claim 10, wherein the six Arabic letters having a dot are coded as a character code preceded by a predetermined one of the first, second and third level codes.

12. The system of claim 11, wherein the classifying means comprises means for specifying each received character as a character of the type that joins to the preceding or following character in a given word, a character of the type that does not join the following character in a given word but does join the preceding character, a character of the type that does not join either the preceding or following character, a character of the type that does not cause the movement of the display to another space, or a character of the type that specifies a typewriter command.

13. The system of claim 12, wherein said adapter comprises means for generating an 8-bit code specifying the stored character code as one of a plurality of possible characters including all Arabic characters and forms thereof, standard operation commands, punctuation, numerals and diacritical marks, wherein the possible characters and character forms number over one hundred

14. The system of claim 10, wherein said adapter comprises means for generating an 8-bit code specifying the stored character code as one of a plurality of possible characters including all Arabic characters and forms thereof, standard operation commands, punctuation, numerals and diacritical marks, wherein the possible characters and character forms number over one hundred.

15. The system according to claim 10, wherein the character and level codes comprise 5 bit digital words.

16. The system according to claim 10 or claim 15, wherein the means for receiving the multi-bit codes comprises means for alternatively receiving multi-bit codes from a remote code generating means and wherein the adapter further comprises means for remotely transmitting the multi-bit codes to be received by the receiving means.

17. The system according to claim 10 wherein the first display comprises an LED display and the second display comprises a printer.

18. A method of word processing Arabic-Farsi languages comprising the steps of:
a. generating a succession of multi-bit character codes each representing one of an Arabic character of the Arabic Farsi language and a plurality of other characters including numerals, punctuation and command characters, wherein the character code for each Arabic character is independent of the form thereof by providing a keyboard having a plurality of keys each corresponding to at least one of a single form of an Arabic character and the plurality of other characters;
b. converting the form independent character codes into the proper language form for display by i. dividing the characters into one of at least three groups and inserting one of at least three multi-bit level codes into the succession of character codes to identify at least one associated character code as representing characters of one of the three groups of characters, ii. receiving and storing the codes for at least two successive characters;
iii. classifying each received character represented by the stored codes as one of a plurality of predetermined character types, and iv. generating a form code for each received Arabic character identifying same as one of four Arabic character forms in response to the classification of the character immediately preceding and immediately following the Arabic character under consideration; and c. displaying the last entered character in a first display without regard to form and displaying each Arabic character in its proper form in a second display in response to the received character codes and the form code for each of a succession of characters in successive positions by displaying the successive characters in the same position in response to an indication that a received character is of a predetermined type for which the display position is not to change.

19. The method of claim 18, wherein the six Arabic letters having a dot are coded by inserting a predetermined one of the first, second and third level codes before the character code therefor.

20. The method of claim 19 wherein the step of classifying comprises specifying each received character as a character of the type that joins to the pre-ceding or following character in a given word, a character of the type that does not join the following character in a given word but does join the preceding character, a character of the type that does not join either the preceding or following character, a character of the type that does not cause the movement of the display to another space, or a character of the type that specifies an operation command.

21. The method of claim 20, wherein the step of converting comprises generating an 8-bit code specifying the stored character code as one of a plurality of possible characters including all Arabic characters and forms thereof, standard operation commands, punctuation, numerals and diacritical marks, wherein the possible characters and character forms number over one hundred.

22. The method of claim 18 wherein the step of converting comprises generating an 8-bit code specifying the stored character code as one of a plurality of possible characters including all Arabic characters and forms thereof, standard operation commands, punctuation, numerals and diacritical marks, wherein the possible characters and character forms number over one hundred.

23. The method according to claim 18, wherein the character and level codes comprises 5 bit digital words.

24. The method according to claim 18 or claim 23, wherein the step of receiving the multi-bit codes comprises alternatively receiving multi-bit codes from a remote code generating means and wherein the step of converting further comprises remotely transmitting the multi-bit level and character codes.

25. The method according to claim 18, wherein the first display comprises an LED display and the second display comprises a printer.

26. The system of claim 10, wherein the classifying means comprises means for specifying each received character as a character of the type that joins to the preceding or following character in a given word, a character of the type that does not join the following character in a given word but does join the preceding character, a character of the type that does not join either the preceding or following character, a character of the type that does not cause the movement of the display to another space, or a character of the type that specifies a typewriter command.

27. The method of claim 18 wherein the step of classifying comprises specifying each received character as a character of the type that joins to the preceding or following character in a given word, a character of the type that does not join the following character in a given word, but does join the preceding character, a character of the type that does not join either the preceding or following character, a character of the type that does not cause the movement of the display to another space, or a character of the type that specifies an operation command.