AutoCAD® 2002 - Autodesk

takes advantage of this flexibility in input format and does not generate a file
exactly like one generated by AutoCAD.
In the case of an error in using DXFIN to load, AutoCAD reports the error with
a message indicating the nature of the error and the last line processed in the
DXF file before the error was detected. This may not be the line on which the
error occurred, especially in the case of errors such as the omission of
required groups.
Binary DXF Files
The ASCII DXF file format is a complete representation of an AutoCAD drawing
in an ASCII text form, and is easily processed by other programs. In addition,
AutoCAD can produce or read a binary form of the full DXF file and
accept limited input in another binary file format.
The SAVE and SAVEAS commands provide a Binary option that writes binary
DXF files. Such a file contains all of the information present in an ASCII DXF
file but in a more compact form that takes, typically, 25 percent less file
space. It can be read and written more quickly (typically, five times faster) by
AutoCAD. Unlike ASCII DXF files, which entail a trade-off between size and
floating-point accuracy, binary DXF files preserve all of the accuracy in the
drawing database. (AutoCAD Release 10 was the first version to support this
form of DXF file; it cannot be read by older versions.)
A binary DXF file begins with a 22-byte sentinel consisting of the following:
AutoCAD Binary DXF
Following the sentinel are pairs (group, value) as in an ASCII DXF file but represented
in binary form. The group code is a 2-byte binary value (1-byte in
DXF files prior to AutoCAD Release 14), and the value that follows is one of
the following:
■
■
■
A 2-byte integer with the least significant byte first and the most significant
byte last
An 8-byte IEEE double-precision floating-point number stored with the
least significant byte first and the most significant byte last
An ASCII string terminated by a 0 (NULL) byte
158 | Appendix A Drawing Interchange File Formats