IBMDOS.COMOne of two hidden system files that make up IBM's PC-DOS. The other is IBMBIO.COM. These two system files are loaded into memory when the computer is booted. They process the instructions in CONFIG.SYS, then load COMMAND.COM and finally process the instructions in AUTOEXEC.BAT. The MS-DOS counterparts of these system files are IO.SYS and MSDOS.SYS.