## Input/Output Device Driver Reference

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### Asynchronous (RS232-C) Communications Device Driver

The Asynchronous Communications (ASYNC) device driver enables OS/2 applications to utilize the Serial Communications (RS232-C) device hardware . The physical device driver allows an application program in OS/2 session to support duplex communications while the device driver:

Services the RS232-C port in an interrupt-driven manner
Provides transmit and receive queues
Provides different automatic control modes for the modem control signals
Provides logical data stream flow control (XON/XOFF) for transmit and receive operations

The user will normally want to use the physical ASYNC device driver either in conjunction with the spooler (for serial printers only) or with an application program that uses the RS232-enabling capabilities of the physical ASYNC device driver coupled with a serial device attached to the system.

The user installs the physical ASYNC device driver by adding a DEVICE= statement to the CONFIG.SYS file.