The header also includes information needed to read and write the particular file: references to locations in the file where other sections begin section lengths flags to indicate how much of the file content is encrypted and a stream of handle references to other structures. Other header variables include: default units and styles for the drawing drawing size limits coordinate systems to use for spatial positioning a project name creation and modification dates and times, etc. The first "variable" in the header is the code used to identify the DWG format version (see File type signifiers below). Header: This section always comes first in the DWG file.Cyclic redundancy checksums (CRC) are used extensively for error detection.Ī typical DWG file will include at least the following sections: See Notes below for more on handles in DWG files. Handle references may indicate ownership or simply be pointers to other structures. Internal connections in the drawing file use identifiers for objects (including the graphical entities) known as "handles." Objects declare their own handles and may refer to other objects via handle references. This contains component graphical elements (known as entities) and other objects that support the editing and rendering of drawings.
The primary substance of a drawing is in a section with name AcDb:AcDbObjects.
The syntactic structure of a DWG drawing file includes sections and section substructures. See Notes below, for information about the chronological versions of the AutoCAD application and associated versions of the DWG format. The compilers of this resource have chosen to describe the DWG family of formats in a single document. Autodesk lists past versions of DWG at AutoCAD Release History. One more recent version, associated with AutoCAD 2018 through 2020, is in use. The format has been updated frequently as the AutoCAD product has been enhanced.Īs of January 2020, PRONOM had records for 19 chronological versions, none of which is publicly documented by AutoDesk. AutoCAD 1.0 was released in 1982, but the origins of the DWG format are from the late 1970s, when it was the native format for a CAD package called Interact. DWG is a compact binary format that stores and describes the content of 2D and 3D design data and metadata. DWG is the proprietary native file format for AutoCAD, one of the most popular computer-assisted design (CAD) packages.
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