| MAC OS Resource Format | |
| Apple | |
| Ads |
RSRC package file format was used by older Apple Mac OS systems. Developers decided to shelve RSRC files when Mac OS X (version 10.0, codename Cheetah) debuted in 2001 and earlier when system beta version (Kodiak) released year earlier.
RSRC files stored text data along with images or icons. RSRC package files were typically used for creating graphical themes for the desktop. RSRC files could also hold custom data and be used by other applications.
Mac OS
| .a | Unix Static Object Code Library Format |
| .a2w | Alice Program World Format |
| .actx | DS Game Maker Action Description Format |
| .ada | ADA Language Source Code Format |
| .addin | Microsoft Visual Studio Addin Format |
| .ads | Ada Package Specification |
| .agi | Asterisk Gateway Interface Format |
| .alb | Alpha Five Data Dictionary |