## Pen for OS/2 Device Driver Reference

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### Stand-Alone Operation

Pen device drivers created with the Pen for OS/2 Developer's Toolkit are not intended to be used in a system without the Pen for OS/2 system extension. The OS/2 2.1 MOUSE.SYS, without the Pen for OS/2 Device Driver Services, supports only a single device-dependent driver with a single locator device and no extended information packet. Other logical device types are not supported.

It is possible for a pen device driver to run without the Pen for OS/2 system extension. The locator Pen for OS/2 Device Driver Service interface is similar to the OS/2 2.1 MOUSE.SYS IDC interface. The MOUSE.SYS statement in the CONFIG.SYS must include a TYPE= for the pen device driver. The TYPE= in the MOUSE.SYS statement in the CONFIG.SYS must not be present on a Pen for OS/2 system if the device driver has registered with DevHlp_ RegisterDeviceClass. The pen device driver's AttachDD IDC entry point must be used for the standard MOUSE.SYS protocol. Being called at the AttachDD entry point by MOUSE.SYS can be used to determine the device driver's mode of operation. An AttachDD to MOUSE.SYS must be performed during READ_ ENABLE to locate the MOUSE.SYS IDC entry point. The MOUSE.SYS interrupt packet must be used instead of the extended information packet.

DevHlp_RegisterDeviceClass can be called on an OS/2 2.1 system without the Pen for OS/2 system extension, but it will be ignored, and the driver entry point will not be called. The Pen for OS/2 device driver is not supported in previous versions of the OS/2 operating system.

If the pen device driver has multiple locator devices, either they must share the MOUSE.SYS interrupt packet or only one device can be supported. The IDC entry point, as defined in the device driver header, must fan out the calls to all locator device entry points if the interrupt packet is shared.

There is no requirement for interrupt packet sharing, and it will require additional programming in the device driver. Supporting both interfaces might be useful if the device driver will be used on OS/2 systems without the Pen for OS/2 system extension.