Different regions of operation of transistor?

In BJT due to the presence of two junctions, each junction can be operated in forward or reverse bias leading to three different regions of operation. Transistor when used as a switch in logic gates will be operated in extreme regions of input output characteristics in which both regions will be forward biased or reverse biased which are called saturation and cut off regions of operation simultaneously. Transistor when used as amplifier is operated in active region in which input junction will be forward biased and output junction will be reverse biased. Other region inverse active region is of less importance in practice.