The LED display is made up of seven segments, and they are lit up in a certain fashion to display numbers. The individual segments are named from a to g and h is the name of the dot. Each segment is lit by its corresponding pin. The function of the 7447 IC is to light the appropriate segment depending on the BCD digit input to the IC. In other words it is a BCD to 7-segment decoder. For example, if a BCD 0001 is input then the output of the decoder will light the corresponding LEDs to display the number ‘1’. The BCD numbers are provided by the BCD counter as shown. With each clock, the output counts up.