"IOProcs" are input/output procedures. MMPM/2 uses these things to be able to understand various file formats and storage types.

IOProcs are really a very abstract concept and hard to understand. Basically, this concept allows MMPM/2 to understand new media formats without a programmer having to rewrite MMPM/2 together. So to make all &os2; applications understand a new media format, one "only" has to write an IOProc. These must reside in a DLL and then get registered with MMPM/2 through the MINSTALL program.

IOProcs can either read files, or write them, or both, depending on how lazy the programmer was.

The "FourCC" stands for "four-character code" and is used to correlate an IOProc to a file format and to find a codec for an IOProc, if necessary. See the next page for details.

There are several "IOProc types":

With "file" IOProcs, there are three main media types: