## Physical Device Driver Reference

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### Character Device Drivers

These drivers support I/O for character (or stream or byte) oriented devices. These devices are usually characterized by one or more of the following:

Reading data is destructive (non-persistent)
Accessing data is sequential
Accessing data on byte boundaries
Utilizing Programmed I/O (PIO)

A character device driver usually has names such as SCREEN$, KBD$, LPT1 or COM2. Applications talk to character device drivers by issuing a DosOpen on the specific device name and then issuing DosRead, DosWrite or DosDevIOCtl calls using the returned handle.

A character device driver can support more than one device by having multiple device headers that each indicate a different device name. Character device drivers are sometimes used as generic extensions of the OS /2 kernel because they do not unnecessarily take up a drive letter yet have the properties of running in the kernel. For additional information on specific character device drivers, refer to the OS/2 Input/Output Device Driver Reference.