T(a > b) + T(a = b) + T(a < b) = 1

Many common logical operations, like selecting and comparing, and the behavior of many simple mechanisms, like a light or a lock, can be expressed by truth values. [Chapter 4], on punch-card mechanisms, contains a number of examples.

pronoun, variable

In ordinary language, a pronoun, like “he,” “she,” “it,” “the former,” “the latter,” is a word that usually stands for a noun previously referred to. A pronoun usually stands for the last preceding noun that the grammar allows. In mathematics, a variable, like “a,” “b,” “x,” “m₁,” “m₂” closely resembles a pronoun in ordinary language. A variable is a symbol that usually stands for a number previously referred to, and usually it stands for the same number throughout a particular discussion.

multiplicand, dividend, augend, etc.

In the
Equation		The Name
of a is:		The Name
of b is:		The Name
of c is:
a + b = caugendaddendsum
a - b = cminuendsubtrahendremainder
a × b = cmultiplicandmultiplierproduct
a ÷ b = cdividenddivisorquotient

Augend and addend are names of registers in the Harvard Mark II calculator ([see Chapter 10]).

subtraction by adding, nines complement

Two digits that add to 9 (0 and 9, 1 and 8, 2 and 7, 3 and 6, 4 and 5) are called nines complements of each other. The nines complement of a number a is the number b in which each digit of b is the nines complement of the corresponding digit of a; for example, the nines complement of 173 is 826. Ordinary subtraction is the same as addition as of the nines complement, with a simple correction; for example, 562 less 173 (equal to 389) is the same as 562 plus 826 (equal to 1388) less 1000 plus 1.