Patent GB-458800-A (GB)
Title: Improvements in or relating to calculating machines for performing division
IPC: G06F7/46
Filed: 1935-06-28
Abstract: 458,800. Calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd., Victoria House, Vernon Place, Southampton Row, London. June 28, 1935, No. 18556. Convention date, June 29, 1934. [Class 106 (i)] Division is performed automatically in a calculating machine by a method which consists in performing successive subtractions until a negative difference is obtained and in eliminating the extra cycle required to add the divisor, except in the case of the final operation producing a remainder, by the operation of adding nine-tenths of the divisor in the first operation of the next series of subtraction operations. The invention is shown applied to a record card controlled machine the arrangements of the sections and the manner in which they are driven being similar to the multiplying machine described in Specification 405,031. The machine Figs. 1, and 1a includes a card handling section an accumulator DD for the dividend, a register DR for the divisor, an additional accumulator À9DR in which nine times the divisor is calculated, a printing section PR, a punching mechanism, a column shift and control relay section CS, CR, and a set of impulse emitters 12-14 and distributers 15, 16, and cam contacts CC, and FC. The card-handling section comprises a contact roller 87, Fig. 2, with co-operating reading brushes 21 and advance reading brushes 22 with card lever contacts 23, 24. Upon a card entering this section the brushes 22 read the divisor and dividend fields and control pre-setting mechanism to select the denominational entry of the factors into the register and accumulators. Following this circuit selection operation the brushes 21 read the card and the factors are entered. There is a double entry of the divisor into the register DR and into the accumulator 9DR ; as this accumulator has one more denomination than the register, the entry is ten times the divisor. The complement of the divisor in the register is then read out and added to the entry in the accumulator to obtain nine times the divisor. Concurrently with this operation the complement of the divisor is added into the dividend accumulator DD. After this operation further subtraction operations are performed until the accumulator reaches a negative quantity. The occurrence of " 9 " in one of the highest denominations is sensed and initiates a column shift action whereupon nine-tenths of the divisor is read out of the accumulator À9DR and added to the dividend accumulator. If the amount is still negative the column shift controller again functions and nine-tenths is added in the next lower denomination otherwise further subtraction operations occur. The final operation results in adding the divisor to the negative amount thereby obtaining the remainder. The quotient is obtained in the highest denomination of the accumulator DD by virtue of the carry-over actions in the accumulator. A typical example of the process is shown in Fig. 6. The result is recorded on the card by the use of the known form of punching mechanism ; it may also be recorded on a record sheet the printing mechanism being called into operation to print the dividend and divisor prior to the card passing the brushes 21. The number of denominations in the quotients part depends on the setting of a quotient place mechanism which serves to connect the quotient part and the remainder part separately to the punching and printing mechanisms.