ASAtomASAtom objects are hashed tokens that Acrobat uses in place of strings to optimize performance (it is much faster to compare ASAtom objects than strings). ASAtom methods convert between strings and ASAtom objects.
 ASCabASCab objects (cabinets) can be used to store arbitrary key-value pairs. The keys are always NULL-terminated strings containing only low-ASCII alphanumeric characters.
 ASCallbackCallbacks allow Acrobat to call functions in a plug-in. The core API provides macros to create and destroy callbacks. These include ASCallbackCreateProto(), ASCallbackCreateReplacement(), and ASCallbackCreateNotification() (defined in PICommon.h), and ASCallbackDestroy(). These macros (which eventually call the macro ASCallbackCreate()) allow compilers to perform type checking, eliminating an extremely common source of bugs. It is sometimes necessary for a plug-in to call ASCallbackCreate() directly; for example, when it is passing function pointers without typedefs to Mac OS toolbox routines.
 ASDateDate objects represent a particular date and time. All date objects are guaranteed to give accurate representation of UTC time (not adjusted for leap seconds, as the addition of leap seconds to the international calendar does not happen according to a well-defined rule).
 ASExtensionAn ASExtension represents a specific plug-in. A unique ASExtension object is created for each plug-in when it is loaded. If the plug-in fails to initialize, the ASExtension remains, but is marked as dead. The ASEnumExtensions() method allows you to iterate over all plug-in objects.
 ASFileThe ASFile interface encapsulates Acrobat's access to file services. It provides a common interface for Acrobat, applications, and plug-ins to access file system services on different platforms, and enables you to provide your own file storage implementations.
 ASFileSysAn ASFileSys is a collection of functions that implement file system services, such as opening files, deleting files, reading data from a file, and writing data to a file. Each ASFileSys provides these services for one class of devices. Acrobat has a built-in ASFileSys that services the platform's native file system. Acrobat on Windows includes an additional ASFileSys that services the OLE2 IStorage/IStream interfaces. Plug-ins may create additional ASFileSys objects to service other file systems. For example, a plug-in could implement an ASFileSys to access PDF files stored in a document database or to access PDF files across a serial link.
 ASPlatformPathAn opaque object used to retrieve a platform-specific path object. This object was added in Acrobat 6.0 to improve device-independent path referencing.
 ASStmAn ASStm is a data stream that may be a buffer in memory, a file, or an arbitrary user-written procedure. You typically would use an ASStm to extract data from a PDF file. When writing or extracting data streams, the ASStm must be connected to a Cos stream. ASStm methods allow you to open and close streams, and to read and write data.
 ASTextAn ASText object holds encoded text.
 ASTimeSpanAn ASTimeSpan object represents an exact time span, measured in seconds. The internal representation uses 64-bit signed integers (to avoid the 2038 problem caused by 32-bit representation). Negative timespans are allowed.
 ASUUID An object containing data and methods supporting a universal unique identifier (UUID) for the current user or the current session.
 Errors Errors object.
 Fixed_Point_Math Fixed point math object.
 General General AS layer objects.
 HFT_and_HFT_Server HFT and HFT server objects.
 Memory_Allocation Memory allocation object.
 String_Encoding Host encoding object.