Boolean Algebra is a way of describing a circuit in the form of a mathematical formula. While this may sound difficult, it actually isn't difficult at all. The AND function is represented by a large dot (times sign), the OR function is represented by a plus sign, and the INVERTER function is represented by a line over top of the input.

This equation states that output A is equal to input B AND input C. The above symbol is the schematic symbol for an AND gate.

This equation states that output D is equal to input E OR input F. The above symbol is the schematic symbol for an OR gate.

This equation states that output G is equal to INVERTED H. The above symbol is the schematic symbol for an INVERTER gate.

Boolean Algebra formulas do become more complicated, and can be manipulated by following specific rules that will be discussed later. These three symbols will permit us to write equations for more complicated devices.

The above is a two input AND (inputs A and B) and another two input AND (inputs C and D) both going into a two input OR gate who's output is E. The lines connecting the AND gates to the OR gate aren't required if the schematic is drawn so that their outputs are directly connected to the inputs of the OR gate.

The equation for the first AND gate is A*B and the equation for the second AND gate is C*D. Both of these are going into an OR gate who's output is E. Since A*B is one input to this OR gate, and the other is C*D, the equation for E becomes...

E = (A * B) + (C * D)

Note how the formula indicates A*B is one input to this OR gate, and the other is C*D. Consider this other other example.

Both of the inputs to the AND gate are two input OR gates. Remember the formula for an AND gate is input #1*input #2 and the formula for an OR gate is input #1+input #2. Because input #1 of the AND gate is F+G and input #2 is H+I, the formula for J is...

J = (F + G) * (H + I)