DDC/CI (Command Interface) standard was introduced in August 1998. It specifies a means for a computer to send commands to the monitor, as well as receive sensor data from the monitor, over a bidirectional link. Specific commands to control monitors are defined in a separate Monitor Control Command Set (MCCS) standard version 1.0, released in September 1998.
DDC/CI monitors are sometimes supplied with an external color sensor to allow automatic calibration of the monitor's color balance. Some tilting DDC/CI monitors support an auto-pivot function, where a rotation sensor in the monitor enables the operating system to keep the display upright as the monitor is moved between its portrait and landscape positions.
Most DDC/CI monitors support only a small subset of MCCS commands and some have undocumented commands. Many manufacturers did not pay attention to DDC/CI in the past, but now almost all monitors support such general MCCS commands as brightness and contrast management.
DDC/CI standard describes a full suite of bidirectional control protocols - DDC2Ab, DDC2Bi and DDC2B+ - in a single standard and provides a means for packaging Monitor Control Command Set commands.
DDC/CI version 1.1 was adopted in October 2004.
Monitor Control Command Set version 2.0 was adopted in October 2003. A new MCCS V3 was introduced in July 2006, though didn't gain enough industry attention as of yet. The latest release of V2 standard is version 2.2, adopted February 2009.
Read more about this topic: Display Data Channel