OSType (also known as FourCC or ResType) is the name of a four-byte type commonly used as an identifier in Mac OS. The four bytes could in principle have any binary value, though they are usually ASCII or characters from the Mac Roman character set. Mac OS, which stands for Macintosh Operating System, is a range of graphical user interface-based operating systems developed by Apple Computer for the Macintosh computers. ... There are 95 printable ASCII characters, numbered 32 to 126. ... The Mac OS Roman character set Mac-Roman encoding is a one byte character encoding system, traditionally used by Mac OS. In Mac OS X, it has been replaced with Unicode. ...

Macintosh platform

OSType values were used to identify file data format types, as well as the applications that created them. The separation of file types and creators allowed the coexistence of documents of the same format belonging to different applications; it was easy to reassign the ownership of any of these documents to any supporting application, without changing its name or otherwise affecting its contents. A type code is a mechanism used in pre-Mac OS X versions of the Macintosh operating system to denote a files format, in a manner similar to file extensions in other operating systems. ... A creator code is a mechanism used in pre-Mac OS X versions of the Macintosh operating system to link a data file to the application program which created it, in a manner similar to file extensions in other operating systems. ...

OSTypes were also used to identify the types of data in other places besides files: for instance, on the Clipboard or in resources, as well as in AppleEvents. They tended to have common meanings across these uses: for instance, 'TEXT' meant a block of text (encoding unspecified, but usually ASCII or Mac Roman), while 'PICT' meant a QuickDraw picture. A clipboard is small, thin board that is typically slightly larger than a pad of standard sheets of paper, with a large (typically metal) clip at the top. ... The resource fork is a construct of the Mac OS operating system and implemented in all of the filesystems used for system drives on the Macintosh, MFS, HFS and HFS Plus (However later versions of mac OS could read and write to disks in formats that didnt support resourse... Apple Events are the canonical high-level interprocess communication mechanism in Mac OS, first appearing in System 7 and supported by every version since then, including Mac OS X. The starting point is a dynamically-typed, extensible descriptor format called an AEDesc, which is just an OSType code specifying the... Two quickdraws. ...

Four byte identifiers are useful because they can be made up of four human-readable characters with mnemonic qualities, while still fitting in the four byte memory space typically allocated for integers in 32-bit systems. From a memory management standpoint, they're more easy to handle than for example character strings of variable length. Compared to arbitrary 32-bit integer values, they are unambiguous since the byte-order is clearly defined. In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ...

Other uses for OSTypes were:

• as Gestalt selector codes
• as record field IDs and event type and class IDs in AppleEvents
• for identifying components in the Component Manager
• as "atom" IDs in the QuickTime movie and image file formats
• as table IDs in the TrueType font format
• as a localization-independent way of identifying standard folders in the Folder Manager
• in QuickDraw GX, they were used as gxTag types and also as types of collection items in the Collection Manager.

Gestalt is the name of a system call introduced in System 6. ... Apple Events are the canonical high-level interprocess communication mechanism in Mac OS, first appearing in System 7 and supported by every version since then, including Mac OS X. The starting point is a dynamically-typed, extensible descriptor format called an AEDesc, which is just an OSType code specifying the... The Component Manager was one of many approaches to sharing code that originated on the pre-PowerPC Macintosh. ... QuickTime is a multimedia technology developed by Apple Computer, capable of handling various formats of digital video, sound, text, animation, music, and immersive virtual reality panoramic images. ... TrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobes Type 1 fonts used in PostScript. ... QuickDraw GX was a replacement for the QuickDraw graphics engine and Printing Manager, initially released in about January 1995. ...

Other platforms

In 1985 Electronic Arts introduced the Interchange File Format (IFF) meta-format (family of file formats), originally devised for use on the Amiga. These files consisted of a sequence of "chunks" which could contain arbitrary data, each chunk prefixed by a four-byte ID. This article is about the year. ... Interchange File Format (IFF), is a generic file format originally introduced by the Electronic Arts company in 1985 in order to ease transfer of data between software products produced by different companies. ... Interchange File Format (IFF), is a generic file format originally introduced by the Electronic Arts company in 1985 in order to ease transfer of data between software products produced by different companies. ... The Amiga is a family of home/personal computers originally developed by Amiga Corporation as an advanced game console. ...

This IFF was adopted by a number of developers including Apple for AIFF files and Microsoft for RIFF files (which were used as the basis for the AVI and WAV file format). Microsoft and Windows developers refer to their four-byte identifiers as Four Character Codes (FourCC). Apple Computer, Inc. ... Audio Interchange File Format is a file format standard used for storing audio data on PCs. ... Microsoft Corporation (NASDAQ: MSFT, HKEx: 4338) is the worlds largest software company, with 2005 global annual sales of 40 billion US dollars and more than 55,000 employees in 85 countries and regions. ... In music, a riff is an ostinato figure: a repeated chord progression or melodic figure, often played by the rhythm section instruments, that forms the basis or accompaniment of a rock music or jazz composition. ... AVI, an acronym for Audio Video Interleave, is a multimedia container format introduced by Microsoft in November 1992, as part of the Video for Windows technology. ... WAV (or WAVE), short for WAVE form audio format, is a Microsoft and IBM audio file format standard for storing audio on PCs. ... Microsoft Windows refers to a series of operating environments and operating systems created by Microsoft for use on personal computers and servers. ...

Other file formats that make important use of the four-byte ID concept are the Standard MIDI File Format, the PNG image file format, the 3DS (3D Studio Max) mesh file format and the ICC profile format. Musical Instrument Digital Interface, or MIDI, is an industry-standard electronic communication protocol that defines each musical note in an electronic musical instrument such as a synthesizer, precisely and concisely, allowing electronic musical instruments and computers to exchange data, or talk, with each other. ... A PNG image with an 8-bit transparency layer (top), overlayed onto a chequered background (bottom). ... 3D Studio Max (sometimes called 3ds Max or just MAX) is a 3-dimensional vector graphics and animation program, written by Kinetix (a division of Autodesk). ... The International Color Consortium was formed in 1993 by eight industry vendors in order to create a universal color management system that would function transparently across all operating systems and software packages. ...

External links

• FourCC.org -- video codec and pixel format information