Most multimedia applications require file input and output (I/O) — that is, the ability to create, read, and write disk files. Multimedia file I/O services provide buffered and unbuffered file I/O and support for RIFF files. The services are extensible with custom I/O procedures that can be shared among applications.
Most applications need only the basic file I/O services and the RIFF file I/O services. Applications sensitive to file I/O performance, such as applications that stream data from compact disc in real time, can optimize performance by using services to directly access the file I/O buffer. Applications that access custom storage systems, such as file archives and databases, can provide their own I/O procedure that reads and writes elements of the storage system.