---
description: "Learn more about: __m128i"
title: "__m128i"
ms.date: "11/04/2016"
f1_keywords: ["__m128i_cpp"]
helpviewer_keywords: ["__m128i keyword [C++]"]
ms.assetid: bd245d68-862c-46dd-9903-6c67c7c5dbcd
---
# __m128i

**Microsoft Specific**

The **`__m128i`** data type, for use with the Streaming SIMD Extensions 2 (SSE2) instructions intrinsics, is defined in \<emmintrin.h>.

```cpp
// 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)<br/>
[Built-in types](../cpp/fundamental-types-cpp.md)<br/>
[Data Type Ranges](../cpp/data-type-ranges.md)