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System-Specific Predefined Macros

The C preprocessor has several predefined macros whose purpose is to indicate the type of system and machine in use. If your code uses system-specific predefined macros, evaluate whether you really need to use them. In most cases applications need to know the capabilities available on a computer and not the specific system or machine on which the application is running. For example, if your application needs to know whether it is running on a little-endian or big-endian microprocessor, you should use the __BIG_ENDIAN__ or __LITTLE_ENDIAN__ macros or the Core Foundation function CFByteOrderGetCurrent. Do not use the __i386__ and __ppc__ macros for this purpose.

See GNU C 4.0 Preprocessor User Guide for additional information.

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