HyperTalk: Язык программирования для HyperCard

Programming language

HyperTalk is a discontinued high level, procedural programming language created in 1987 by Dan Winkler and used in conjunction with Apple Computer's HyperCard hypermedia program by Bill Atkinson. Because the main target audience of HyperTalk was beginning programmers, HyperTalk programmers were usually called "authors" and the process of writing programs was known as "scripting". HyperTalk scripts resembled written English and used a logical structure similar to that of the Pascal programming language. HyperTalk supported the basic control structures of procedural languages: repeat for/while/until, if/then/else, as well as function and message "handler" calls (a function handler was a subroutine and a message handler a procedure). Data types usually did not need to be specified by the programmer; conversion happened transparently in the background between strings and numbers. There were no classes or data structures in the traditional sense; in their place were special string literals, or "lists" of "items" delimited by commas (in later versions the "itemDelimiter" property allowed choosing an arbitrary character). Code execution typically began as a response to an event such as a mouse click on a UI widget. In the late 1980s, Apple considered The case insensitive language was initially interpreted, but gained just in time compilation with HyperCard 2.0.

HyperCard's primary user interface concept was the card, a display system that emulated an index card. Cards were normally used to store information, similar to a record in a conventional flat file database. The graphical layout of the card was created using the mouse by placing various elements on the card, such as text fields and buttons. A master layout "card" known as the background was shown behind the transparent areas of each card. Objects placed on the background, such as fields and buttons, would be shared as a common layout among several cards, but with card specific content. The collection of cards, backgrounds and the associated data stored in them were stored in a single file known as the stack (of cards). Collectively, all of these data containing objects are referred to as containers. HyperTalk functions, or scripts, were normally stored within the script property available in many of the stack's containers. Scripts could access the properties of a container, corresponding to instance variables, using the get and set instructions. The script property held plain text and had no special properties; scripts could be placed in, and run from, any text container, including string variables, or imported from other stacks using the start using command. A script could even be user provided text typed into an on screen text field. Arbitrary text could be executed using the do command, in a manner similar to Dynamic SQL.

Unlike general rapid application development platforms, HyperCard stacks always looked like stacks the menu bar was HyperCard's and not the programmer's (by default—scripting could add, delete and modify menus), the single window was a fixed size (in early versions), and in certain cases, commands that were central to the operation were part of the application itself, and not directly available in HyperTalk itself. A good example of this was the creation of new cards, which was part of the application, not directly accessible from the HyperTalk language itself. A new card could only be created using the New Card menu item, which could be simulated in code usingdoMenu "New Card". While HyperTalk called into menu commands, menu commands also invoked handlers in HyperTalk. To run custom code when the Copy menu item was selected, one would place a script in the stack using the on doMenu itemName handler, and then examine itemName to see if it was "Copy". HyperTalk also provided script control over the built in drawing tools, simply by scripting the needed changes in paint tools and simulating mouse movements using the drag from start to end and the click at position commands.

Although the HyperTalk language languished just like HyperCard itself, it interest was revived through its plugin protocol, so called External Commands (XCMDs) and External Functions (XFCNs), which were native code containers attached to stacks (as Macintosh specific resources) with a single entry point and return value. XCMDs and XFCNs could be called just like regular message and function handlers from HyperTalk scripts, and were also able to send messages back to the HyperCard application. Some XCMD authors added advanced features like full color support (ColorizeHC, HyperTint, AddColor), multiple special purpose windows (Prompt, Tabloid, Textoid, Listoid, ShowDialog, MegaWindows), drag and drop support and various hardware interfaces to the language.