DED (Doomsday Engine Definition) is the name of the textual definition language of Doomsday 1.x. One syntax to define everything from Particle Generators to Things, in an easy to edit plain text format.

Files in this format are conventionally given the .DED file name extension.

This article provides a high level overview of the definition language, including the most important elements in a .ded file — the definition types themselves.

Typically a .ded file consists of a collection of definitions, either loosely related, or, grouped together according to some organizational structure (usually decided by the mod author).

Note that the order of the definitions in the .ded file affects how Doomsday uses them.

All definition files share a single common syntax in Doomsday. Once learned, the same knowledge can be applied across the board to all definition types.

If you are new to Doomsday modding you'll want to familiarize yourself with DED syntax before going further. (It won't take long as its fairly standard/straightforward).

See also: Altering and copying definitions

Definition files may be specified to the engine for loading in a variety of ways:

• On the command line with the -def option
• Automatically from the auto directory
• Automatically from a PK3 add-on
• Automatically from a WAD add-on
• Included dynamically from another .DED file

See also: Paths on the command line

These articles offer complete walk throughs on how to achieve something very specific within the realms of editing for Doomsday with step-by-step guidance. Plus background information on “why” a certain method has been used.

• Create a "Barrel Monster"
• Create a "Light Thing"
• Use DoomBuilder to edit DED files