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# __m128i
## Microsoft Specific  
 The `__m128i` data type, for use with the Streaming SIMD Extensions 2 (SSE2) instructions intrinsics, is defined in emmintrin.h.  
  
```  
// data_types__m128i.cpp  
#include <emmintrin.h>  
int main() {  
   __m128i x;  
}  
```  
  
## Remarks  
 You should not access the **__m128i** fields directly. You can, however, see these types in the debugger. A variable of type `__m128i` maps to the XMM[0-7] registers.  
  
 Variables of type **_m128i** are automatically aligned on 16-byte boundaries.  
  
> [!NOTE]
>  Using variables of type `__m128i` will cause the compiler to generate the SSE2 **movdqa** instruction. This instruction does not cause a fault on Pentium III processors but will result in silent failure, with possible side effects caused by whatever instructions **movdqa** translates into on Pentium III processors.  
  
 The `__m128i` data type is not supported on ARM processors.  
  
**END Microsoft Specific**  
  
## See Also  
 [Keywords](../cpp/keywords-cpp.md)   
 [Fundamental Types](../cpp/fundamental-types-cpp.md)   
 [Data Type Ranges](../cpp/data-type-ranges.md)