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### 5.10 Additional Floating Types

As an extension, the GNU C compiler supports additional floating types, `__float80` and `__float128` to support 80bit (`XFmode`) and 128 bit (`TFmode`) floating types. Support for additional types includes the arithmetic operators: add, subtract, multiply, divide; unary arithmetic operators; relational operators; equality operators; and conversions to and from integer and other floating types. Use a suffix w or W in a literal constant of type `__float80` and q or Q for `_float128`. You can declare complex types using the corresponding internal complex type, `XCmode` for `__float80` type and `TCmode` for `__float128` type:

         typedef _Complex float __attribute__((mode(TC))) _Complex128;
         typedef _Complex float __attribute__((mode(XC))) _Complex80;

Not all targets support additional floating point types. `__float80` is supported on i386, x86_64 and ia64 targets and target `__float128` is supported on x86_64 and ia64 targets.