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title: "auto Keyword | Microsoft Docs"
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---
# auto Keyword
The `auto` keyword is a declaration specifier. However, the C++ standard defines an original and a revised meaning for this keyword. Before Visual C++ 2010, the `auto` keyword declares a variable in the *automatic* storage class; that is, a variable that has a local lifetime. Starting with Visual C++ 2010, the `auto` keyword declares a variable whose type is deduced from the initialization expression in its declaration. The [/Zc:auto[-]](../build/reference/zc-auto-deduce-variable-type.md) compiler option controls the meaning of the `auto` keyword.  
  
## Syntax  
  
```cpp  
auto declarator ;  
auto declarator initializer;  
```  
  
## Remarks  
 The definition of the `auto` keyword changes in the C++ programming language, but not in the C programming language.  
  
 The following topics describe the `auto` keyword and the corresponding compiler option:  
  
-   [auto](../cpp/auto-cpp.md) describes the new definition of the `auto` keyword.  
  
  
-   [/Zc:auto (Deduce Variable Type)](../build/reference/zc-auto-deduce-variable-type.md) describes the compiler option that tells the compiler which definition of the `auto` keyword to use.  
  
## See Also  
 [Keywords](../cpp/keywords-cpp.md)