Each implementation of C and C++ supports some features unique to its host machine or operating system. Some programs, for instance, need to exercise precise control over the memory areas where data is placed or to control the way certain functions receive parameters. The #pragma directives offer a way for each compiler to offer machine- and operating system-specific features while retaining overall compatibility with the C and C++ languages. Pragmas are machine- or operating system-specific by definition, and are usually different for every compiler.
Pragmas can be used in conditional statements, to provide new preprocessor functionality, or to provide implementation-defined information to the compiler. The Microsoft C and C++ compilers recognize the following pragmas:
