Similarly, you can clear any other regular storage register if you repeat its code in the out-and in-fields. However, a few of the storage registers in the machine have special reset codes, and these may occur in any of the three fields _A_, _B_, _C_. As the result of a recent modification of the machine, you can easily double the number in any storage register. For example, the instruction Double the number in register 321; read the next coding line is coded: 321, 321, 743 Subtracting If the number in switch 741 is to be subtracted from the number in storage counter 321, the instruction is changed into: Take the negative of the number in switch 741; transfer it into storage register 321; read the next line of coding The coding line becomes: 741, 321, 732 By putting 32 in the _C_ field, we cause the number in switch 741 to be subtracted from whatever number is in register 321. We have 2 more choices in adding and subtracting. The value of the number without regard to sign—in other words, its _absolute value_ (see Supplement 2)—may be added or subtracted. The instruction Add the absolute value of is expressed by a _C_ field code 2, and the instruction Add the negative of the absolute value of is expressed by a _C_ field code 1. Multiplying When we wish to multiply one number by another and get a product, we have 3 numbers. We tell the machine about each of these numbers on a separate line of coding. Multiplication is signaled by sending a number into the _multiplicand counter_. The multiplicand counter has an in-code 761. If the multiplicand is in 321, the instruction is: Take the number in 321; enter it as multiplicand; read the next coding line The coding is: 321, 761, 7 On the third following coding line, the multiplier is sent into the _multiplier counter_. If the multiplier is in switch 741, the instruction is: Take the number in 741; enter it as multiplier; read the next coding line The coding is: 741, ——, 7 We do not punch anything in the middle field: the machine is “educated” and “knows” that it has started a multiplication and needs a multiplier, and it expects this multiplier in the third coding line. To have no code for the multiplier counter is, of course, a departure from the general rule, but it saves some punching and permits the use of this space for certain other codes, thus saving some operating time. We need not confuse the 761 in-code for the multiplicand counter with the 761 out-code, which happens to be the out-code of the 25th constant register, because neither can occur in the other’s field. We may, of course, use other registers besides 321 and 741 for supplying the multiplicand and multiplier. To get the product and put it into any storage counter _D_, we use two lines of coding one right after the other: —— —— 6421 8761 _D_ ——