Editing HyperCard (section)

===Externals===
HyperCard can be extended significantly through the use of ''external command'' (XCMD) and ''external function'' (XFCN) modules. These are code libraries packaged in a stack's [[resource fork]] that integrate into either the system generally or the HyperTalk language specifically; this is an early example of the [[Plug-in (computing)|plug-in]] concept. Unlike conventional plug-ins, these do not require separate installation before they are available for use; they can be included in a stack, where they are directly available to scripts in that stack.

During HyperCard's peak popularity in the late 1980s, a whole ecosystem of vendors offered thousands of these externals such as HyperTalk compilers, graphing systems, database access, Internet connectivity, and animation. Oracle offered an XCMD that allows HyperCard to directly query Oracle databases on any platform, superseded by [[Oracle Card]]. BeeHive Technologies offered a hardware interface that allows the computer to control external devices. Connected via the [[Apple Desktop Bus]] (ADB), this instrument can read the state of connected external switches or write digital outputs to a multitude of devices.

Externals allow access to the Macintosh Toolbox, which contains many lower-level commands and functions not native to HyperTalk, such as control of the serial and ADB ports.