The following predefined macros are provided to facilitate porting applications between platforms. All platform-related predefined macros are unprotected and can be undefined or redefined without warning unless otherwise specified.
| Predefined macro name | Description | Predefined value | Predefined under the following conditions |
|---|---|---|---|
| _BIG_ENDIAN, __BIG_ENDIAN__ | Indicates that the platform is big-endian (that is, the most significant byte is stored at the memory location with the lowest address). | 1 | Always predefined. |
| __powerpc, __powerpc__ | Indicates that the target is a Power® architecture. | 1 | Predefined when the target is a Power architecture. |
| __PPC, __PPC__ | Indicates that the target is a Power architecture. | 1 | Predefined when the target is a Power architecture. |
| __unix, __unix__ | Indicates that the operating system is a variety of UNIX. | 1 | Always predefined. |