Patent GB-1090761-A (GB)
Title: Calculator
IPC: G06F15/02
Filed: 1964-10-23
Abstract: 1,090,761. Keyboard calculators. FRIDEN Inc. Oct. 23, 1964 [Oct. 28, 1963], No. 43417/64. Heading G4A. An electronic keyboard operated calculator comprises a magnetic drum 1 (Fig. 1) having five tracks, three (Fig. 2) for producing timing pulses, a fourth (Fig. 6) for storing in pulse count notation form four interlaced 25-digit numbers and a fifth (Fig. 6) for storing temporarily the multiplier and quotient in multiplications and divisions, said calculator enabling shifts within registers, transfers between the four number registers and the four rules of arithmetic to be performed on the contents of these registers by means of a single read head 4 two write heads 2 and 3, a single up counter 9 and a single down counter 16. The storage arrangement in track 4 is such that the number of 1 bits in each digit position is one greater than the corresponding decimal digits of the stored numbers. Fig. 6 shows the interlaced arrangement of the track 4 registers whereby digits of the same order of significance are stored adjacent each other. The four registers are referred to as T1 (temporary store 1), T2 (temporary store 2), ACC (Accumulator register) and ENT (Entry register). A " dead time " is provided between the start position H 2  and end position H 1  of the drum. The single read head and two write heads are each spaced apart by three digit positions. Addition of two adjacent registers is obtained by reading into up counter 9 for each order of significance the bits of the first register followed by the bits of the next register with no intermediate clearing. The result -order-by-orderis then transferred to down counter 16 and written back on to the drum in the position previously occupied by the first register. For subtraction, down counter 16 is used to obtain the complement of the minuend. Provision is made for carrying and borrowing. Multiplication and division are similarly obtained by successive additions or subtractions under the control of the program signal generator. Shifting of the contents of a register to left or to right and transfers between registers is obtained simply by reading the digits of the selected register into up counter 9, transferring to down counter 16 and rewriting at the required new positions. These operations are described at length in the Specification with reference to Figs. 8-31 (not shown). Numbers are entered into ENT register by successive depressions of the required digit keys of a digit signal generator (illustrated diagrammatically in Fig. 8, not shown), said generator being coupled to the up counter 9. The contents of ENT register may be transferred to ACC register by depression of the FFA key of a function signal generator (illustrated diagrammatically in Fig. 10, not shown). Keys marked T1 and T2 (in Fig. 10) are provided for temporarily storing the contents of the ACC register in register T1 or T2 respectively, recall from these registers to ENT register being by means of keys marked R 1  and R 2 . Keys for the four rules of arithmetic (the operands being the numbers stored in registers ACC and ENT), shifting of ENT register to left and right and a clear key are provided (Fig. 10, not shown). The timing track outputs are shown in Fig. 2 wherein track 1 produces the start and end signals H 2  and H 1 , track 2 (R) signals define the start and end of each digit time slot and track 3 signals define the bit times (1200 between H 2  and H 1 ). The contents of the registers may be displayed, for example on a cathode ray tube.