text: Common uses One of the most well-known uses of FourCCs is to identify the video codec or video coding format in AVI files. Common identifiers include DIVX, XVID, and H264. For audio coding formats, AVI and WAV files use a two-byte identifier, usually written in hexadecimal (such as 0055 for MP3). In QuickTime files, these two-byte identifiers are prefixed with the letters "ms" to form a four-character code. RealMedia files also use four-character codes, however, the actual codes used differ from those found in AVI or QuickTime files.
  Other file formats that make important use of the four-byte ID concept are the Standard MIDI File (SMF) format, the PNG image file format, the 3DS (3D Studio Max) mesh file format and the ICC profile format.
  Four-character codes are also used in applications other than file formats, for example:
  UEFI Forum for vendor in the ACPI ID Registry
  ACPI specification defines four-character identifiers in ACPI Source Language (ASL)
  Synopsys to tell component ID via registers of an IP (DesignWare collection)
  Other uses for OSTypes include:
  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 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.
  Enumeration constants in Apple APIs (as an integer; host endianess)
  "OSStatus" error codes in certain libraries, such as QuickTime (as an integer; host endianess)