---
page_type: sample
description: "Enumerates Plug-n-Play RS-232 devices that are compliant with the current revision of Plug and Play External COM Device."
languages:
- cpp
products:
- windows
- windows-wdk
---

# Serenum sample

Serenum enumerates Plug-n-Play RS-232 devices that are compliant with the current revision of Plug and Play External COM Device. It loads as an upper filter driver to many different RS-232 device drivers that are compliant with its requirements and performs this service for them.

Serenum implements the Serenum service and its executable image is serenum.sys.

Serenum is an upper-level device filter driver that is used with a serial port function driver to enumerate the following types of devices that are connected to an RS-232 port:

- Plug and Play serial devices that comply with Plug and Play External COM Device Specification, Version 1.00, February 28, 1995.

- Pointer devices that comply with legacy mouse detection in Windows.

The combined operation of Serial and Serenum provides the function of a Plug and Play bus driver for an RS-232 port. Serenum supports Plug and Play and power management.

Windows provides Serenum to support Serial and other serial port function drivers that need to enumerate an RS-232 port. Hardware vendors do not have to create their own enumerator for RS-232 ports. For example, a device driver can use Serenum to enumerate the devices that are attached to the individual RS-232 ports on a multiport device.

## File Manifest

| File | Description |
| --- | --- |
| Enum.c | Functions that enumerate external serial devices (the main purpose of this driver) |
| Pnp.c | Plug and Play support code |
| Power.c | Power support code |
| Serenum.c | Basic driver functionality |
| Serenum.h | Local header with defines, prototypes |
| String.c  | String handling support, mainly ASCII to UNICODE functionality |
| Serenum.rc | Resource script |

For more information, see [Features of Serial and Serenum](https://docs.microsoft.com/windows-hardware/drivers/serports/features-of-serial-and-serenum).