7–segment Display. An LED or Light Emitting Diode, is a solid state optical pn-junction diode which emits light energy in the form of photons. … Each of the seven LEDs is called a segment because when illuminated the segment forms part of a numerical digit (both Decimal and Hex) to be displayed.
Generally seven segment displays are available in 10 pin package. While eight pins correspond to the eight LEDs, the remaining two pins (at middle) are common and internally shorted.
The 7 segment display come in two configurations, namely, Common cathode and Common anode.
In Common cathode configuration, the negative terminals of all LEDs are connected to the common pins. The common is connected to ground and a particular LED glows when its corresponding pin is given high.
In Common anode configuration, the common pin is given a high logic and the LED pins are given low to display a number.