GB1216821A - Number entry system for digital data processors - Google Patents

Abstract

1,216,821. Number entry into data processors. MATSUSHITA ELECTRIC INDUSTRIAL CO. Ltd. 7 Jan., 1969, No. 974/69. Heading G4A. In a number entry system for a digital data processor, successive digits are entered into an input register at the position corresponding to a marker signal in an auxiliary register, the contents of the input register being left-shifted by one digit position for each digit entry prior to the establishment of the decimal point and the marker signal being right-shifted by one digit position for each digit entry after the decimal point establishment. The input and auxiliary registers, and a third register, are circulating shift registers. The digits are decimal digits from a keyboard, converted to binary-coded form and serialized by gates for entry into the input register at a time-position when the marker signal 1111 reaches a particular point in the auxiliary register. The marker signal is inserted into the auxiliary register at a time-position determined by a pre-set decimal point selector switch when the first digit is entered. The " establishment " of the decimal point referred to is the pressing of a decimal point key during number entry. When the number of digits after the decimal point specified by the decimal point selector switch have been entered, any further attempted entry will shift out and so delete the marker signal, preventing entry. During arithmetic operations, the input register is used for addend, subtrahend, multiplicand or divisor, the auxiliary register for multiplier or quotient, and the third register acts as an accumulator. A first modification has a marker signal of 1, converted to 1111 by ORing the outputs of taps' on the auxiliary register which is partly a chain of bit delays. A second modification has a single loop of shift registers in which the contents of the three previous registers are interleaved in different time-slots.