The Input/output system
All hardware related routines are defined in IO.SYS and MSDOS.SYS files. These files are loaded in the memory first when computer boots in MS-DOS. These files are used to communicate with the computer’s hardware.
The Command processor
It is present in COMMAND.COM file. It is loaded after input/output system files are loaded into the memory. It translates all commands given by the user at the command prompt to the operating system for execution.
Utilities
These are separate add-ons, which increase the capability and offering from MS-DOS. Utilities like Defrag, Backup and Restore helps in better utilization of disk drives.
