Chapter 5 -- BLOCKS Section

The following group codes apply to block entities. For information about abbreviations and formatting used in this table, see "Formatting Conventions in This Reference."

Block group codes
Group codes Description


Entity type (BLOCK)



102 (optional)

Start of application-defined group "{application_name". For example, "{ACAD_REACTORS" indicates the start of the AutoCAD persistent reactors group.

application-defined codes (optional)

Codes and values within the 102 groups are application defined

102 (optional)

End of group, "}"


Soft-pointer ID/handle to owner object


Subclass marker (AcDbEntity)


Layer name


Subclass marker (AcDbBlockBegin)


Block name


Block-type flags (bit coded values, may be combined):
1 = This is an anonymous block generated by hatching, associative dimensioning, other internal operations, or an application.
2 = This block has non-constant attribute definitions (this bit is not set if the block has any attribute definitions that are constant, or has no attribute definitions at all).
4 = This block is an external reference (xref).
8 = This block is an xref overlay.
16 = This block is externally dependent.
32 = This is a resolved external reference, or dependent of an external reference (ignored on input).
64 = This definition is a referenced external reference (ignored
on input).


Base point
DXF: X value; APP: 3D point

20, 30

DXF: Y and Z values of base point


Block name


Xref path name


Block description (optional)

The UCS in effect when a block definition is created becomes the WCS for all entities in the block definition. The new origin for these entities is shifted to match the base point defined for the block definition. All entity data is translated to fit this new WCS.

Model Space and Paper Space Block Definitions

Three empty definitions always appear in the BLOCKS section. They are titled *Model_Space, *Paper_Space and *Paper_Space0. These definitions manifest the representations of model space and paper space as block definitions internally. The internal name of the first paper space layout is *Paper_Space, the second is *Paper_Space0, the third *Paper_Space1, and so on.

Model Space and Paper Space Entity Segregation

The interleaving between model space and paper space no longer occurs. Instead, all paper space entities are output, followed by model space entities. The flag distinguishing them is the group code 67.