Understanding Strings In COM

Understanding Strings In COM

By Davide Marcato

ANSI and Unicode, char and wchar_t were not enough: COM introduced several new string data types, and the differences and the process of conversion are not always obvious to the uninitiated. This article clarifies the situation once and for all for the benefit of raw COM, ATL and MFC programmers.

Strings, i.e. vectors of alphanumeric characters, are and have always been a fundamental data type in every programming language and platform. Whereas the computer itself prefers to deal with numbers, human beings prefer messages of text to sequences of binary, hexadecimal or even decimal digits. This implies that whenever a piece of software needs to interact with the user (or signal some notable events) some kind of string treatment is likely to come into play.