Control Data 3100 Reference Manual page 171

MULTIPLICATION
Binary multiplication proceeds according to the following rules:
OxO
=
0
Ox 1
=
0
1 xO
=
0
1 x 1
=
1
Multiplication is always performed on a bit-by-bit basis. Carries do not result from mul-
tiplication, since the product of any two bits is always a single bit.
Decimal example:
multiplicand
multiplier
partial products
product
14
~
J
28
'\. 14 (shifted one place left)
16810
The shift of the second partial product is a shorthand method for writing the true value 140.
Binary example:
multiplicand (14) 1110
multiplier
(12)
1lQL
partial products {
0000
0000 shift to place
1110 digits in proper
1110 columns
product
(16810)
101010002
The computer determines the running subtotal of the partial products. Rather than
shifting the partial product to the left to position it correctly, the computer right shifts
the summation of the partial products one place before the next addition is made. When
the multiplier bit is "1", the multiplicand is added to the running total and the results
are shifted to the right one place. When the multiplier bit is "0", the partial product sub-
total is shifted to the right (in effect, the quantity has been multiplied by 102).
DIVISION
The following examples shows the familiar method of decimal division:
divisor
14
13\ 185
_13 _ _
quotient
dividend
55 partial dividend
~
3 remainder
B-4