OS2DOS.COM
| Company type | System file |
|---|---|
| Industry | Computer software |
| Products | IBM PC DOS, DR-DOS |
IBMDOS.COM serves as the core kernel file for both IBM PC DOS and DR-DOS, being loaded by the DOS BIOS component within IBMBIO.COM during system startup. It encompasses hardware-agnostic operating system elements, including integrated support for FAT12 and FAT16 file systems, with later versions extending compatibility to FAT32. Additionally, it provides the essential DOS API utilized by software applications.
This kernel is present in versions ranging from PC DOS 1.0 up to PC DOS 7.10, as well as in DR DOS 5.0 and subsequent releases—except for DR-DOS 7.06, where its functionality is incorporated into IO.SYS. The equivalent role in MS-DOS is fulfilled by MSDOS.SYS, whereas DR-DOS versions 3.31 through 3.41 employed DRBDOS.SYS. For interoperability purposes, IBM's OS/2 version 1.0 temporarily adopted the IBMDOS.COM filename to align with Microsoft's OS2DOS.COM kernel naming convention.
Typically found in the root directory of the boot drive (commonly C:\), IBMDOS.COM is assigned hidden, read-only, and system attributes to prevent unintended execution, which could result in system failure. Starting with DR-DOS 7.02, this file incorporates a compact COM-style stub that safely outputs version information if run improperly.
Within Digital Research's framework, this kernel is known as the BDOS (Basic Disk Operating System), a designation introduced by founder Gary Kildall in 1975 for CP/M and sustained across later DRI operating systems. The portion of code handling FAT file systems is termed FDOS.