A seven segment display is composed of seven elements that individually on or off can be combined to produce simplified representations of the numbers 0-9.
There are two types of 7-segment displays:
- Common Anode with all the LED anodes connected together. These need a display driver with outputs which become low to light each segment. The common anode is connected to +Vs.
- Common Cathode with all the LED cathodes connected together. These need a display driver with outputs which become high to light each segment. The common cathode is connected to 0V.
The segments in a 7-segment display are referred to by the letters A-G, as shown in the picture. Some displays have a dot to allow for the representation of a decimal point.