1. Overview of the Display Manager

	Workstation (SPARC station, DEC station, or HP)
	LAN support
	The UNIX operating system
	The X windows interface and its components: X server, X client, and X window manager.
	EPICS Channel Access software

DM is "user-friendly." The operator's interaction with the workstation was designed to be as easy and intuitive as possible by using a graphical interface that allows the operator to "see" the status of the system and to control it with ease. The graphical interface presents information both quantitatively and qualitatively. For example, data for the same process variable can be presented either textually through an object such as a text-update object or graphically through an object such as a meter.

Displays provide DM's graphical interface. A display is configured using EDD and then stored in a display list file. Display list files often have the extension .dl and are usually placed in a directory named dl, which is usually a sub-directory in an application directory (the .dl extension is just a convention). Display list files are binary files. EDD also has the ability to produce ASCII display list files, which should have the extension .adl and which are primarily used for upward compatibility between OPI versions.

IMPORTANT: DM does not use ASCII display list files. If you try to run DM with an ASCII file, the following message will appear on the command line: Not a binary display file? Couldn't read file <filename> No display name <filename> --exiting dm

A display contains a number of objects that control or monitor process variables. Objects can be static or dynamic. Dynamic objects are configured in EDD to connect to channels when opened by DM. Such objects do the actual controlling and monitoring of process variables in DM. The term channel refers to a field in an EPICS record (though only the record need be specified, in which case the VAL field is implied). DM connects to channels using Channel Access client requests.

To run DM, you must have a basic familiarity with the X Windows interface.