Patent GB-1252859-A (GB)
IPC: G06F15/02
Filed: 1970-03-16
Abstract: 1,252,859. Calculators; data storage. WANG LABORATORIES Inc. 16 March, 1970 [21 March, 1969], No. 12441/70. Headings G4A and G4C. An electronic calculator system comprises a keyboard unit having a plurality of manually actuable control elements including ten control elements for numerical values from 0 through 9 and other control elements for instruction values, logic responsive to the operation of the control elements for generating predetermined codes, each such code having the same number of digits and representing either a numerical value or an instruction value, and recording means operable in two modes, a learn mode in which actuation of the control elements initiates the recording of indications representative of the codes upon a recording medium, and a normal mode in which the medium is sensed for the indications and signals responsive to the sensed indications are produced to control the operation of the calculator system, an input register being coupled between the keyboard logic, the recording medium and an arithmetic unit. The recording medium is a magnetic tape loop in a cartridge which can be inserted into the keyboard unit which also includes a display and is connected by a cable to a portable electronics package. A plug socket in the keyboard unit permits optional I/O devices (including stores) to be attached. The codes are of 6 bits and can be transferred parallel-by-bit to a buffer register from the keyboard, I/O devices or a shift register, and parallel-by-bit from the buffer register to a calculation circuitry, I/O devices or shift register. The shift register is used for transferring a 6-bit code, preceded and followed by a framing bit, to or from the magnetic tape serial-by-bit, each bit being supplied to or from the tape as a pulse of one of two durations depending on the bit value. An error indication is produced on read-out from the tape if the lagging framing bit does not reach its stage in the shift register within a predetermined interval of the leading framing bit reaching its stage. Shift pulses are produced from the bits on readout. The keyboard selects whether the machine will be controlled by (programme) codes entered from the keyboard as they are entered, or whether these codes will be stored on the tape, or whether the tape will be read to control the machine. Most codes result from respective keys but a set of bit manual switches are also provided to enter special codes. Execution of codes is done continuously, or one each time a " step " key is pressed, according to the setting of an auto/step switch. Codes keyed on to the tape can be displayed (each code as two octal digits) and keying errors corrected by re-keying and overwriting. A reflective strip on the magnetic tape is sensed to indicate a reference position. Some programme codes perform a zero, sign or overflow test, causing the next two codes in the programme to be skipped or not according to the result. An erase key (in learn mode) causes the tape to be driven and erased until the reflective strip has been sensed twice. A consecutive pair of codes on the tape may specify " mark X " (X, the second code, being one of 64 numbers). If a " search X " pair of codes are encountered during normal (run) mode, this latter X is transferred via the shift register into the buffer register and the tape driven without programme execution until a " mark X " is detected with the same X (detected by comparing the shift register, holding the X of " mark X ", with the buffer register) whereupon programme execution continues. Thus jump to a subroutine can be accomplished. A " search and return X " pair of codes has the same effect as a " search X " regarding jumping to a subroutine but at the end of the subroutine (marked by a " return " code) return is effected. A counter (reset to zero when the reflective strip is sensed during tape drive) counts the " search and return " codes encountered. On jump, the current count is saved in a register, and when the " return " code is executed at the end of the subroutine, the tape is driven until the count again equals that in the register, thus returning to the point from which the jump was made. Tape drive is always in the same direction.