The multimedia input/output (MMIO) file services are an extension of the base OS/2 file services. Designed to be simple, fast, and flexible, the MMIO services-functions, messages, and data structures-enable an application to access and manipulate multimedia data files. These files contain a variety of media elements (images, graphics, digital audio, and video) that are in different file formats; for example, RIFF, AVC, and M-Motion.

MMIO services provide a consistent programming interface so that an application can refer to these files, read and write data to the files, and query the contents of the files, without having to know anything about the specific format of the files. MMIO services strengthen a program's portability, as well as data compatibility, by insulating the application from the underlying file formats.

Note: As a general comment, all fields in MMIO services data structures that are not used in a given function must be initialized to NULL. Flags that are not used, and bits not used within flags, must be set to 0.