Writing a Recognizer

A recognizer is a dynamic-link library (DLL) that interprets lines of ink as characters and symbols. Version 2.0 of the Pen API allows a pen-based application to install multiple recognizers and use them selectively. Each recognizer should specialize in recognizing a particular set of symbols instead of trying to handle many different types. Besides keeping the recognizer code manageable, this approach lets an application choose among several available recognizers to fulfill its current recognition needs.

The recognizer developer must know both sides of the interface between application and recognizer. The foregoing chapters, particularly Chapter 5, "The Recognition Process," should be read before venturing into this one.

Such a developer should also have some familiarity with the coding requirements of a DLL. For information about how to write a DLL, see the Guide to Programming manual in the Microsoft Windows Software Development Kit. In addition, the "Writing a Dynamic-Link Library for Windows" chapter in the MASM version 6.1 Programmer's Guide offers valuable information about DLL coding requirements.

This chapter describes the framework of a recognizer DLL and the functions it must export. The final section presents a sample recognizer called SREC. The source file for SREC resides in the SAMPLES\PEN\SREC subdirectory.

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