2.1 Boolean Algebra
Boolean algebra
operates on the principle that any logical statement must be definitively
either true or false; there are no intermediate states. A simple illustration
of this is a light switch, which can only be either ON or OFF at any given
moment, never both simultaneously.
Table 1 will then present the
binary conditions and their alternative representations.
Table 1. Binary logic and other representation
Logic 1 |
Logic 0 |
True |
False |
High |
Low |
ON |
OFF |
YES |
NO |
Open |
Close |
+5v |
0v |
The fundamental rules
governing Boolean algebra are called postulates. The most basic of these
postulates deal with the TRUE or FALSE states of a single variable. Through
logical deduction, examining all possible variations of a single variable
(including its relation to itself, 1, and 0), we derive various equalities or
identities. These identities are mathematical statements that are logically
equivalent and thus interchangeable within a logic equation without changing
the result. The standard mathematical equality symbol (=) is used in Boolean
algebra to denote this equivalence.
The core postulates of
Boolean algebra are derived from three basic logic functions: AND, OR, and
COMPLEMENTATION. These postulates are expressed as algebraic equations using
specific symbols for these functions.
Boolean algebra was
first developed by George Boole in 1854 as a systematic approach to logic.
Later, in 1938, C.E. Shannon adapted this concept into "switching
algebra," a two-valued Boolean algebra used to model the behavior of
bistable electrical switching circuits.