The OS/2 Boot Manager enables different operating systems to co-reside on the same computer. The user selects the operating system to boot when the computer is turned on. For example, DOS, AIX, and the OS/2 operating system can co-reside on the same machine. There can also be a previous version of the OS/2 operating system on the machine co-existing with the current version of the operating system.
Each operating system has its own partition and each partition is managed by the appropriate file system for the operating system that owns it. A DOS partition has a FAT file system. An OS/2 partition can have either a FAT file system or HPFS. An AIX partition will use the AIX file system to manage its partition.
Note: FAT partitions that follow HPFS partitions on the same physical disk cannot be accessed when using DOS because DOS stops at the first partition it does not recognize.