1300-112 is part of the Methode-McDonnell Douglas commercial avionics message protocol, which is a series of messages that end users use to send commands and receive status information from avionics systems in an aircraft. This protocol is used for a wide range of communication functions, including navigation, communication, and control. The messages in the protocol consist of a number of value-value relations, where each value corresponds to a specific command or status information. The messages in the protocol are organized into groups so that they can be referenced and recognized easily.