HyperCard

HyperCard is a software application and development kit for Apple Macintosh and Apple IIGS computers. It is among the first successful hypermedia systems predating the World Wide Web. HyperCard combines a flat-file database with a graphical, flexible, user-modifiable interface. HyperCard includes a built-in programming language called HyperTalk for manipulating data and the user interface. This combination of features – a database with simple form layout, flexible support for graphics, and ease of programming – suits HyperCard for many different projects such as rapid application development of applications and databases, interactive applications with no database requirements, command and control systems, and many examples in the demoscene. HyperCard was originally released in 1987 for $49.95 and was included for free with all new Macs sold then. It was withdrawn from sale in March 2004, having received its final update in 1998 upon the return of Steve Jobs to Apple. HyperCard runs in the Classic Environment, but was not ported to Mac OS X. HyperCard is based on the concept of a 'stack' of virtual 'cards'. Cards hold data, just as they would in a Rolodex card-filing device. Each card contains a set of interactive objects, including text fields, check boxes, buttons, and similar common graphical user interface (GUI) elements. Users browse the stack by navigating from card to card, using built-in navigation features, a powerful search mechanism, or through user-created scripts. Users build or modify stacks by adding new cards. They place GUI objects on the cards using an interactive layout engine based on a simple drag-and-drop interface. Also, HyperCard includes prototype or template cards called backgrounds; when new cards are created they can refer to one of these background cards, which causes all of the objects on the background to be copied onto the new card. This way, a stack of cards with a common layout and functionality can be created. The layout engine is similar in concept to a form as used in most rapid application development (RAD) environments such as Borland Delphi, and Microsoft Visual Basic and Visual Studio. The database features of the HyperCard system are based on the storage of the state of all of the objects on the cards in the physical file representing the stack. The database does not exist as a separate system within the HyperCard stack; no database engine or similar construct exists. Instead, the state of any object in the system is considered to be live and editable at any time. From the HyperCard runtime's perspective, there is no difference between moving a text field on the card and typing into it, both operations simply change the state of the target object within the stack. Such changes are immediately saved when complete, so typing into a field causes that text to be stored to the stack's physical file. The system operates in a largely stateless fashion, with no need to save during operation. This is in common with many database-oriented systems, although somewhat different from document-based applications. The final key element in HyperCard is the script, a single code-carrying element of every object within the stack. The script is a text field whose contents are interpreted in the HyperTalk language. Like any other property, the script of any object can be edited at any time and changes are saved as soon as they were complete. When the user invokes actions in the GUI, like clicking on a button or typing into a field, these actions are translated into events by the HyperCard runtime. The runtime then examines the script of the object that is the target of the event, like a button, to see if its script object contains the event's code, called a handler. If it does, the HyperTalk engine runs the handler; if it does not, the runtime examines other objects in the visual hierarchy.