Patent GB-1199022-A (GB)
Title: Improvements in or relating to Calculators
IPC: G06F3/02
Filed: 1967-09-19
Abstract: 1,199,022. Digital electric calculator. WANG LABORATORIES Inc. 19 Sept., 1967 [24 Oct., 1966], No. 42603/67. Heading G4A. A calculator comprises a keyboard having keys representing digits 0 to 9 and instructions arranged to produce a code unique to each key, two independently controllable accumulator storage registers, each storing numerical values, a unit displaying the contents of one of the registers, an arithmetic unit performing addition and subtraction upon operands ranging in value from 0 to 9, a store of logarithmic constant values and associated means for addressing and reading out of the store selected ones of the constant values, and a control unit including a source of clock pulses, a cycle control and subsidiary control elements and arranged to control the operation of the storage registers, the arithmetic unit and the store of logarithmic constant values in response to the instruction codes. General.-The keyboard enables entry of digits, control of arithmetic operations, the performance of the operations e<SP>x</SP>, loge X, #X and X<SP>2</SP> to be performed and various operations of clearing and recalling from appropriate registers to be performed. A core memory holds Work register W, Right and Left Accumulator registers A 0 , A 1  and a log register L. Digits from the keyboard are entered in the Work register and automatically displayed. Operation of the log X key causes generation of the natural log of the number in the Work register, the log being stored in the log register and this value is then entered in the Work register. The e<SP>x</SP> key causes generation of the antilog of the number which is then stored in the Work register. An ENTER key causes the logs of digits entered to be held in the log register, successive logs being added and the antilog of the result being generated when the a X= key is pressed and stored in the Work register. The core registers each hold 16 b.c.d. digits, the least significant digit holding the decimal point position, the most s.d. holding the sign. Only 10 of the 14 digits of the number are displayed on the screen. Each digit can be individually addressed and arithmetic operations are done serially, each digit being treated in parallel, the particular digit being operated on being determined by an R or a T counter. A D-switch determines the source of data read to the memory. A digit read out of the memory is initially stored in an E register and may be transferred to a G register, display, the adder or back to the memory. The arithmetic unit is supplied with one operand from the E register and the other from a source determined by the B switch. Each digit received by the B switch is applied to a 9's complement matrix enabled if subtraction operations are required. The sum from the adder is applied to a binary to b.c.d. converter to determine whether any carries exist, a CAS flip-flop being provided to store resulting carries for addition to the next digit, the sum being returned to the memory. Memory.-The memory comprises a set of cores (Fig. 6) forming four registers each holding 16 four-bit words, one word being formed by the four black cores shown. Each register is determined by a bit XG 1  applied to an X decoder and a bit XG 2  applied to a Y decoder. The two least significant bits of the R or #R or T registers are applied to the X decoder and the two most significant bits to the Y decoder. Each decoder produces a signal on one out of 8 lines X 0 -X 7 , Y 0 -Y 7  to enable four cores for the reading and writing of a word. An inhibit signal DG determines the nature of data read into a core. Whenever any of the signals DG 1,2,4,8  is "1" a "0" is written into the appropriate enabled core, otherwise a "1" is written. Log generator.-The log generator comprises a diode matrix fixed memory containing the natural logs of a set of twelve constants, half the natural logs of the same set and twice the natural logs of the same set. The contents of the T register determine which of the constants is to be used and the R register determines which digit. Display unit.-The display unit comprises 10 digit display tubes plus a sign indicator tube. Each tube has ten cathodes, corresponding cathodes in each tube being coupled together. Only one tube anode is energized at any one time as determined by the contents of the T register. Each digit is sequentially transferred, under the control of the T register from the W register to the E register, which controls the cathode selection. Flow charts are given indicating the operations performed by the computer under control of counters. The computer operates in a series of b modes determined by a b counter producing ten major b modes. Signals applied by the counter to AND gates (Figs. 18-22, not shown) producing control signals depending on the state of the computer.