DXF Group Codes
CLASSES Section

The group codes described in this section are found only in DXF files.

The CLASSES section holds the information for application-defined classes whose instances appear in the BLOCKS, ENTITIES, and OBJECTS sections of the database. It is assumed that a class definition is permanently fixed in the class hierarchy. All fields are required.

The following is an example of the CLASSES section of a DXF file:

  0
SECTION
  2
CLASSES


Beginning of CLASSES section



  0
CLASS
  1
<class dxf record>
  2
<class name>
  3
<app name>
90
<flag>
280
<flag>
281
<flag>


Repeats for each entry













  0
ENDSEC


End of CLASSES section


Each entry in the CLASSES section contains the groups described in the following table.

CLASSES section group codes
Group code Description

0

Record type (CLASS). Identifies beginning of a CLASS record.

1

Class DXF record name. These should always be unique.

2

C++ class name. Used to bind with software that defines object class behavior. These are always unique.  

3

Application name. Posted in Alert box when a class definition listed in this section is not currently loaded.

90

Proxy capabilities flag. Bit coded value that indicates the capabilities of this object as a proxy.
0 = No operations allowed (0)
1 = Erase allowed (0x1)
2 = Transform allowed (0x2)
4 = Color change allowed (0x4)
8 = Layer change allowed (0x8)
16 = Linetype change allowed (0x10)
32 = Linetype scale change allowed (0x20)
64 = Visibility change allowed (0x40)
127 = All operations except cloning allowed (0x7F)
128 = Cloning allowed (0x80)
255 = All operations allowed (0xFF)
32768 = R13 format proxy (0x8000)

280

Was-a-proxy flag. Set to 1 if class was not loaded when this DXF file was created, and 0 otherwise.

281

Is-an-entity flag. Set to 1 if class was derived from the AcDbEntity class and can reside in the BLOCKS or ENTITIES section. If 0, instances may appear only in the OBJECTS section.

AutoCAD registers the classes listed in the following table (note that this may not be a complete list of the classes found in a DXF file depending on the applications currently in use on your system).

Default class values
DXF Record Name
Code 1		 C++ Class Name
Code 2		 Code
90		 Code
280		 Code
281

DICTIONARYVAR

AcDbDictionaryVar

0

0

0

HATCH

AcDbHatch

0

0

1

IDBUFFER

AcDbIdBuffer

0

0

0

IMAGE

AcDbRasterImage

127

0

1

IMAGEDEF

AcDbRasterImageDef

0

0

0

IMAGEDEF_REACTOR

AcDbRasterImageDefReactor

1

0

0

LAYER_INDEX

AcDbLayerIndex

0

0

0

LWPOLYLINE

AcDbPolyline

0

0

1

OBJECT_PTR

CAseDLPNTableRecord

1

0

0

OLE2FRAME

AcDbOle2Frame

0

0

1

RASTERVARIABLES

AcDbRasterVariables

0

0

0

SORTENTSTABLE

AcDbSortentsTable

0

0

0

SPATIAL_INDEX

AcDbSpatialIndex

0

0

0

SPATIAL_FILTER

AcDbSpatialFilter

0

0

0