Patent GB-662767-A (GB)
Title: Improvements in and relating to calculating machines
IPC: G06F7/544
Filed: 1949-01-14
Abstract: 662,767. Statistical apparatus. BRITISH TABULATING MACHINE CO., Ltd. Jan. 14, 1949 [Jan. 16, 1948], No.. 1092/49. Class 106 (i). A machine for performing multiplication and division comprises a multidenominational divisor register, a multidenominational dividend register, means for comparing one or more digits of the divisor and dividend values and means for effecting a relative column shifting between the divisor and dividend values, the divisor and dividend resisters each comprising a first and second entry receiving device, means controlled by the value represented in the first entry receiving device for entering into the second entry receiving device that value increased by one, means controlled by the value represented in the second entry receiving device for entering into the first entry receiving device the value registered in the second device, the operation of both devices being such that an entry therein supersedes a prior entry, cycling means for causing the first and second entry receiving devices to operate alternately for a predetermined number of times and initiating means for bringing into operation the cycling means. In the described embodiment a combination A of multiplication and division (-XC) is per- B formed by the apparatus, and when straight division or multiplication is required the appropriate factor (C or B respectively) is, in effect, given the value 1. The example is used in describing the operation of the apparatus. Factor entry. The factors are read from a record card 10, Fig. 1, by sensing brushes 12 which pass over the data positions in the order 9, 8, 7 ... 1, 0. The completion of a circuit through a card hole causes energization of a relay (EA - in the case of the dividend, EB - for the divisor and multiplier) allocated to the card column. Each' digit is to be entered on coded relays arranged in circuits as shown in Figs. 2 and 3. There are five sets of relays A, B, C, D, F in each denominational order, and there are ten such denominational orders (Fig. la, not shown). The entry of the data in the example chosen is shown diagram-. matically in Fig. 5. In the machine cycle (first column, Fig. 5) each data position comprises an "a" period, when cam contacts M4, Fig. 1, are closed to energize a relay CB6 and connect the supply line 15 with a line a, and a " b" period when, with a make-beforebreak arrangement, the line 15 is connected to the b line upon de-energization of the relay CB6, and during this latter period the cardsensing circuits are operative. In each denominational order, Fig. 2 and 3, the appearance of a pulse on line a, Fig. 3, after the energization of the associated EB relay, completes a circuit through contacts CFc, the centre contacts EBb, and the b contacts of the code relays B (4 and 1) to energize the code relay C(1), (Fig. 2). Such a registration is indicated by a " 1 " at the top right hand of Fig. 5, following an " X " which represents the sensing of a hole in the card. During the next " b " period a pulse on the line b, Fig. 2, completes a circuit through contacts R5d and the b contacts of C( 1 ) to energize the relay B(1), Fig. 3, thus transferring the digit unchanged to the B relays (cf. Fig. 5); during the next a period the impulse on line a, Fig. 3, is transmitted through the changed B(1) contacts to energize the relay C(2). In the case of the dividend the initial entry is made in the D relays, and then transferred to the A relays. This building up of the factors continues in the manner indicated in Fig. 5 until the " 0 " position in the card cycle is reached. Column shift. During stages " 0," " 11 " and " 12 " means operate to align the dividend (518) and the divisor (793) preparatory to an algebraic addition. Control of this process is exercised by a comparing unit, Fig. 4, comprising two relay-controlled networks operating to determine whether the dividend is greater, equal to, or less than half the divisor, and also whether the dividend is greater, equal to, or less than one-and-a-half times the divisor. Whenever the dividend is greater than 1¢  times the divisor, summation occurs without column shift; when the dividend lies between 1¢ times the divisor and ¢ the divisor, summation occurs followed by column shift; when the dividend is less than ¢ divisor (as indicated in the final column, Fig. 5, for steps 0, 11 and 12) column shift alone is performed. In preparation for the first subtraction (algebraic addition) the divisor 793 and multiplier 419 are transferred, at the " 0 " step, from the C relays to the B relays in the form of 9's complements, the result of the summation (performed by a relay-controlled network) being entered into the D relays which then contain the remainder, or next dividend, in the higher denominations, and the result, subject to adjustment by further computation, in the lower denominations. After an operation following a condition : dividend <(1¢ X divisor, dividend >¢ X divisor, the signs of the multiplier and divisor on the one hand and the dividend on the other hand, are reversed, e.g. at step 14, the multiplier and divisor are transferred in their true form to the B relays while the dividend takes the form of a 9's complement. As the dividend, entered in the higher denominations of the A relays, becomes progressively smaller, whilst the number of digits in the result, which is entered in the lower denominations of the A relays increases a so-called denomination splitting device (represented by the line SP, Fig. 5) causes the split to be progressively shifted to the left. The illustration of the progress of the problem, as applied to the apparatus, is continued from Fig. 5 to Fig. 5a (not shown); the essential arithmetical process is set out in Fig. 6. The registers A, B, C, D, F comprise relays settable alone or in combination in accordance with a 1, 2, 4, 5 code. Binary code relay counters are employed for counting the number of places in the answer and initiating a rounding off operation in accordance with pre-arranged plugging. The answer readout device takes the form of series of lamps in the described embodiment but any current responsive readout device could be used.