The Alpha edition of the compiler defines three keywords: _ _unaligned, _ _int64, and _ _ptr64. To ensure portable source code, use conditional compilation so that the x86 edition does not read these keywords. For example, you can prevent the x86 edition of the compiler from seeing _ _unaligned by creating a macro, _ _unaligned, that is defined as an empty string when compiling for the x86 platform. See Working with Data Alignment Issues in Chapter 3 for an example.
The _ _int64 keyword is recognized by the x86 edition of Visual C++ but is not supported by the integrated debugger. Therefore, its use is not particularly recommended on the x86 platform.