The file system is the component of the operating system that supports storing information on mass storage devices, such as hard disks and diskettes. Applications view a file as a logical sequence of data; the file system manages the physical locations of data on the storage device for the application and specifies how the device and the stored information are formatted.

The file system also manages file I/O operations. Applications use file system functions to open, read, write, and close disk files. File system functions enable an application to maintain the disk that holds the files-volumes, directories, and files on the disks of the computer. Applications also use OS/2 file system functions to perform I/O operations to pipes and peripheral devices connected to the computer, such as the printer.

The file system also supports redirection of input and output, for example redirecting output from the display to a disk file or to the printer.

There are two types of file systems supported by the OS/2 operating system. The first is the File Allocation Table (FAT) file system. The FAT file system is the file system used by DOS The second type of file system supported by the operating system is the installable file system (IFS). Installable file systems are external to the base operating system and are loaded by the operating system when the computer is started. The High Performance File System (HPFS) included with the OS/2 operating system is an installable file system.