Abstract: In a keyboard operation two sequential keystrokes are used for generation of a character code. A rule is set up according to which some preset combinations of two sequential keystrokes are valid and others are not. The rule is implemented by storing the validity conditions into a table in a control unit. According to a preferred rule the second key to be operated must be located in a column to the right of the column where the first key is located, otherwise an error signal will be generated. The method is preferably used for a one hand keyboard with three times four keys.

Abstract: An address word (N) for addressing a memory (2) comprises an exponent field (P) that defines on one hand the number of basic data units or accesses to be made to a memory, on the other a number by which a second field (M) in the address word is modified, the memory initially being addressed by the modified second field.

Abstract: Generation of a character code for an alphabetic character is performed by depressing at least two keys in a sequence. The code is generated when the last key is depressed and the other keys in the sequence still are pressed, or when all keys in the sequence are released. Numerical character codes are generated by depressing only one key per character. A logic and storage means is provided having a number of registers, code converting tables and control circuits for storing the history of depressed keys and for generating character codes.

Abstract: Generation of a character code for an alphabetic character is performed by depressing at least two keys in a sequence. The code is generated when the last key is depressed and the other keys in the sequence still are pressed, or when all keys in the sequence are released. Numerical character codes are generated by depressing only one key per character. A logic and storage means is provided having a number of registers, code converting tables and control circuits for storing the history of depressed keys and for generating character codes.