---
description: "Learn more about: Microsoft Extensions"
title: "Microsoft Extensions"
ms.date: "11/04/2016"
helpviewer_keywords: ["Microsoft extensions to C/C++"]
ms.assetid: 68654516-24ef-4f33-aae2-175f86cc1979
---
# Microsoft Extensions
*`asm-statement`*:\
**`__asm`** *`assembly-instruction`* **`;`**opt\
**`__asm {`** *`assembly-instruction-list`* **`} ;`**opt
*`assembly-instruction-list`*:\
*`assembly-instruction`* **`;`**opt \
*`assembly-instruction`* **`;`** *`assembly-instruction-list`* **`;`**opt
*`ms-modifier-list`*:\
*`ms-modifier`* *`ms-modifier-list`*opt
*`ms-modifier`*:\
**`__cdecl`**\
**`__fastcall`**\
**`__stdcall`**\
**`__syscall`** (reserved for future implementations)\
**`__oldcall`** (reserved for future implementations)\
**`__unaligned`** (reserved for future implementations)\
*`based-modifier`*
*`based-modifier`*:\
**`__based (`** *`based-type`* **`)`**
*`based-type`*:\
*`name`*