The mechanical nature of the first typewriter was such that only one key could be operated at any one time. Also, each key generated only one character. The shift mechanism was later introduced to permit each key to generate two characters. For reliable operation of the keyboard using the touch method, a total of 36 keys could be operated. However, some reduction in reliability was accepted in exchange for an expanded set of 44 keys. This permitted a maximum character set of 88 characters. Many keyboards today incorporate 48 keys, giving a character set of 96 characters. Reliable and fast operation of mechanical typewriters appears to be limited to a set of less than 100 characters.
Electronic keyboards in present usage suffer no such mechanical limitations as above outlined. Common today is the use of multiple shift keys. Two shift keys permit the standard 88 character set to be expanded to 132. Three shift keys permit the generation of 174 characters. The salient fact to be noted is that keys may now be operated in combinations much as a piano is played. The one-peck-at-a-time (OPAT) keyboard has given way to the combinational keyboard.
One such combination keyboard appears in FIG. 1. Base 11 carries keys 1, 2, 4, 8, DP (decimal point), SP (space), Z (zero), a, A, and the Greek letter alpha. The first five keys are positioned to fall naturally under the tips of the fingers of the right hand of the average operator. The second five keys are positioned to fall naturally under the fingers of the left hand.
While combinational keyboards may be used to generate the characters of the Arabic numeral set and the Phoenician alphabet set, certain advantages are realized through retirement of these time honored sets and using the keyboard to generate "Computer Compatible Characters" (CCC'S) of the type discussed in copending Application Ser. No. 593,434 and entitled COMMUNICATION SYSTEM USING BINARY COMPATIBLE CHARACTERS. The complete character used in conjunction with the present keyboard appears in FIG. 2. The character is composed of nine line elements and a dot. The DP and SP elements comprise two lines each. Each element corresponds to a respective key of the keyboard. Each character comprises a subset of the elements of the complete character. A total of 1023 such characters are possible. This last fact demonstrates the tremendous advantage of the combinational keyboard over the OPAT unit. With the former, 100 characters per key are generated. With the latter, only 2 characters per key are generated.
FIG. 3 is a code sheet relating CCC's to conventional characters. The following are noted:
1. Characters which may be generated by the fingers of the right hand only, appear along the top.
2. Characters which may be generated by the left hand only, appear along the left edge.
3. The numerals 1 to 15 may be generated by the fingers of the right hand (without the thumb). The 0 is special and will be dealt with in detail later.
4. The most used mathematical operators are generated by operating the thumb key for the right hand in combination with the numeral keys. This permits mathematics to be handled largely by the right hand only--freeing the left hand for other usage.
5. Including the "a" key into the combinations forms the lower case alphabet.
6. Including the "A" key into the combinations forms the upper case alphabet.
7. Including the "alpha" key into the combinations forms the Greek alphabet.
8. Including both the "a" and "A" keys into the combinations forms a set of punctuation marks.
9. The numerals plus the DP element may be considered a base-32 numbering system. The other elements may be added in succession to form base-64, base-128, base-256, base-512, and base-1024 systems.
10. The third line of the table presents three operational commands--
SP--Space command. A printer would normally respond to this command by leaving a blank space. However, electronically the command is represented by a code element rather than a blank. For the remaining two characters in this row, the SP element is printed.
T--Tabulation. A printer would move to the next printed column upon receipt of this character.
LF--Line Feed. A printer would advance one line and move to the left margin upon receipt of this character.
11. Of the total of 1023 characters provided, only a few of the possible assignments have been made. An italicized alphabet might be added. Or better, a host of phonemes might be represented.
The 0 (zero) has been entered three places in the table. Properly a 0 is represented by a complete absence of character elements as indicated by the 0 in Col. 1, of the table. However, such an absence cannot be distinguished from a blank space. Consequently in printed matter the 0 is represented by the high dot of FIG. 2 (Col 1, Line 4 of the table). The third 0 of FIG. 3 will be discussed later.