A seven-segment display (SSD) is a display device packaged in a single IC chip and composed of a group of seven bar-shaped LEDs. Some seven-segment displays may come with a decimal point (DP). Different numbers and letters may be formed by powering selected LED elements. SSDs come in various packages and pin arranges.

Configurations

Common Anode SSD

Common cathode SSD

There are two basic configurations of seven-segment displays: common cathode (CC) and common anode (CA).

Common Anode

A common anode seven-segment display is one where the anode leads of all the LEDs are tied together. In a CA SSD, power must be supplied to anode that is common to all the segments. Appropriate segments can be lit up by applying ground to them. In this setup a pull-down resistor

Common Cathode

a Common cathode seven-segment display is one where the cathode leads of all the LEDs are tied together.

Basics

The individual segments of a seven-segment display.

The various numbers (and possibly A-F) can be displayed by simply powering the correct segments by either connecting GND or Vcc.