http://www.allaboutcircuits.com/vol_4/chpt_12/4.html
The discrete LED indicators, which we show, could be 7-segment LEDs. Though, there are LSI (Large Scale Integration) devices capable of driving several 7-segment digits. This device accepts data from a microprocessor in a serial format, driving more LED segments than it has pins by by multiplexing the LEDs. For example, see link below for MAX6955