# BOOLEAN ALGEBRA

Boolean (George Boole 1815-1864) algebra considers functions of variables which can assume only two values:

**True**or

**False**

Such values are generally associated with the following symbols:

**1**(indicating True value)

**0**(indicating False value)

In electrical circuits:

a variable may indicate the presence (*positive logic*)
or the absence (*negative logic*)of a predetermined tension value.

Usually Boolean variables are identified with letters as: *A*.

The interaction between variables, determined by logic links (e.g. *B* is true if *A* is false ), is expressed by functions of the following type:

Where
is the negation of A ( i.e. is True if *A* is false).

*Note:*

The first application of Boolean algebra was in the railroad field where Boolean variables indicated the position of rail switches.

The first application of Boolean algebra was in the railroad field where Boolean variables indicated the position of rail switches.