In MS-DOS device drivers are installed and loaded dynamically it implies that they are loaded into memory when computer is started or re-booted and accessed by operating system as needed. Technique has the benefit that it makes addition of a new driver much simpler so that it could be done by relatively unskilled users. The extra merit is that only those drivers that are in fact required need to be loaded in main memory. Device drivers to be loaded are defined in a special file known as CONFIG.SYS that should reside in root directory. This file is automatically read by MS-DOS at start-up of system and its contents acted upon. A list of some device name is as displayed below: 

Device name         Description

con:                       keyboard/screen 

com1:                    serial port1

com2:                    serial port2

lpt1:                       printer port1

A:                          first disk drive

C:                          hard disk drive