The SIT File Format

• Appropriately enough for a file compression utility, StuffIt's principal file extension is an abbreviation for the name of the product. Originally, creating StuffIt archives and decompressing the SIT file format required buying a shareware license directly from Raymond Lau, who paid his way through MIT with his shareware earnings. A SIT file can contain multiple documents of any format. The product became a commercial application in 1990 after Lau transferred the marketing rights to Aladdin Systems.
  
  

The SEA File Format

• "SEA" stands for "Self-Extracting Archive." The SEA format expanded upon SIT files by making it possible to extract their contents without the use of the StuffIt application -- or the widely available StuffIt Expander that resided on every Macintosh user's desktop for generations of the Mac OS. SEA files were slightly larger than SIT files with the same contents because they had to include the programming code necessary for self-extraction.
  
  

The SITX File Format

• In 2002, Aladdin Systems introduced the re-engineered StuffIt X, a new version of the SIT compression algorithm. The "X" in the product name was a nod to the new-generation Mac OS X operating system, though this actually was the second version of StuffIt to run under Mac OS X. StuffIt X could decompress SIT files but earlier generations of StuffIt couldn't cope with SITX files. The new format's file icons carried a small red dot to distinguish them from their predecessor's format. Users complained about the lack of compatibility with existing StuffIt software but welcomed the new format's increased compression -- up to 20 percent, depending on file content -- and its support for long file names and file permissions.
  
  

Into the Future

• In 2005, Smith Micro Software acquired Allume Systems, as Aladdin Systems had renamed itself. Today's StuffIt product line includes Windows versions of the formerly Mac-only utility roster. On the Mac, changes in file formats away from the resource fork/data fork structure that had complicated Mac-to-PC file transmission also reduced the need for StuffIt's resource-fork preserving algorithms and spelled the end of StuffIt's incorporation into the Mac OS. In 2005, with the introduction of Mac OS X 10.4 Tiger, the StuffIt compression engine no longer came bundled with the Mac OS. Today, when a Mac user makes a file archive through her operating system, she's producing a ZIP file, not a SIT or SITX.