Editing ACIS (section)

== File format ==

=== Save File Types ===
ACIS supports two kinds of save files, Standard ACIS Text (SAT), and Standard ACIS Binary (SAB). The two formats store identical information, so the term SAT file is generally used to refer to either when no distinction is needed.

SAT files are ASCII text files that may be viewed with a simple text editor. A SAT file contains carriage returns, white space and other formatting that makes it readable to the human eye. A SAT file has a .sat file extension.

SAB files cannot be viewed with a simple text editor and are meant for compactness and not for human readability. A SAB file has a .sab file extension. A SAB file uses delimiters between elements and binary tags, without additional formatting.

=== Structure of the Save File ===

Specification of SAT format for version 7.0 (circa 2001) has been made publicly available. This allowed external applications, even those not based on ACIS, accessing the data stored in such files. The basic information needed to understand the SAT file format, such as the structure of the save file format, how the data is encapsulated, the types of data written, subtypes and references, is available from this document. However the newer version of ACIS use modified format of SAT files whose specification is not publicly available. Thus reading of modern SAT files requires either using native ACIS library or reverse engineering of the format.

A save file contains:
* a three-line header
* entity records, representing the bulk of the data
* optionally, a begin history data marker
* optionally, old entity records needed for history and rollback
* optionally, an end history data marker
* an end marker

Beginning with ACIS Release 6.3, it is required that the product ID and units be populated for the file header before you can save a SAT file.