(1) Using e-mail , a message is an individual piece of mail.
(2) In computer systems in general, a message is an information unit that the system sends back to the user or system operator with information about the status of an operation, an error, or other condition.
(3) Using some telecommunication or data access methods, a message can be the unit of information or data that is transmitted from one program or user to another.
(4) In messaging , which is the formal exchange of event notification, requests, or replies between programs through a messaging server , a message is data in a specified format that describes an event, a request, or a reply between programs.
(5) In object-oriented programming , a message is the way that one program object requests an action from another object. A message specifies the name of the object to which the request is made, the action (or method ) to be performed, and any parameter or value that needs to be specified for this request.
Conceptually, a message for an object that incorporates all the methods of a automatic vaccuum cleaner might look like this:
VacCleaner Chair Chair1LR
which would request the object VacCleaner to use its chair-cleaning procedure or method on "chair 1" in the living room.