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# &lt;string&gt;
Defines the container template class `basic_string` and various supporting templates.  
  
 For more information about `basic_string`, see [basic_string Class](../standard-library/basic-string-class.md)  
  
## Syntax  
  
```  
#include <string>  
```  
  
## Remarks  
 The C++ language and the C++ Standard Library support two types of strings:  
  
-   Null-terminated character arrays often referred to as C strings.  
  
-   Template class objects, of type `basic_string`, that handle all `char`-like template arguments.  
  
### Typedefs  
  
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|-|-|  
|[string](../standard-library/string-typedefs.md#string)|A type that describes a specialization of the template class `basic_string` with elements of type `char` as a `string`.|  
|[wstring](../standard-library/string-typedefs.md#wstring)|A type that describes a specialization of the template class `basic_string` with elements of type `wchar_t` as a `wstring`.|  
|[u16string](../standard-library/string-typedefs.md#u16string)|A type that describes a specialization of the template class `basic_string` based on elements of type `char16_t`.|  
|[u32string](../standard-library/string-typedefs.md#u32string)|A type that describes a specialization of the template class `basic_string` based on elements of type `char32_t`.|  
  
### Operators  
  
|||  
|-|-|  
|[operator+](../standard-library/string-operators.md#op_add)|Concatenates two string objects.|  
|[operator!=](../standard-library/string-operators.md#op_neq)|Tests if the string object on the left side of the operator is not equal to the string object on the right side.|  
|[operator==](../standard-library/string-operators.md#op_eq_eq)|Tests if the string object on the left side of the operator is equal to the string object on the right side.|  
|[operator<](../standard-library/string-operators.md#op_lt)|Tests if the string object on the left side of the operator is less than to the string object on the right side.|  
|[operator<=](../standard-library/string-operators.md#op_lt_eq)|Tests if the string object on the left side of the operator is less than or equal to the string object on the right side.|  
|[operator<\<](../standard-library/string-operators.md#op_lt_lt)|A template function that inserts a string into the output stream.|  
|[operator>](../standard-library/string-operators.md#op_gt)|Tests if the string object on the left side of the operator is greater than to the string object on the right side.|  
|[operator>=](../standard-library/string-operators.md#op_gt_eq)|Tests if the string object on the left side of the operator is greater than or equal to the string object on the right side.|  
|[operator>>](../standard-library/string-operators.md#op_gt_gt)|A template function that extracts a string from the input stream.|  
  
### Specialized Template Functions  
  
|||  
|-|-|  
|[swap](../standard-library/string-functions.md#swap)|Exchanges the arrays of characters of two strings.|  
|[stod](../standard-library/string-functions.md#stod)|Converts a character sequence to a `double.`|  
|[stof](../standard-library/string-functions.md#stof)|Converts a character sequence to a `float`.|  
|[stoi](../standard-library/string-functions.md#stoi)|Converts a character sequence to an integer.|  
|[stold](../standard-library/string-functions.md#stold)|Converts a character sequence to a `long double`.|  
|[stoll](../standard-library/string-functions.md#stoll)|Converts a character sequence to a `long long`.|  
|[stoul](../standard-library/string-functions.md#stoul)|Converts a character sequence to an `unsigned long`.|  
|[stoull](../standard-library/string-functions.md#stoull)|Converts a character sequence to an `unsigned long long`.|  
|[to_string](../standard-library/string-functions.md#to_string)|Converts a value to a `string`.|  
|[to_wstring](../standard-library/string-functions.md#to_wstring)|Converts a value to a wide `string`.|  
  
### Functions  
  
|||  
|-|-|  
|[getline Template](../standard-library/string-functions.md#getline)|Extract strings from the input stream line by line.|  
  
### Classes  
  
|||  
|-|-|  
|[basic_string Class](../standard-library/basic-string-class.md)|A template class that describes objects that can store a sequence of arbitrary character-like objects.|  
|[char_traits Struct](../standard-library/char-traits-struct.md)|A template class that describes attributes associated with a character of type CharType|  
  
### Specializations  
  
|||  
|-|-|  
|[char_traits\<char> Struct](../standard-library/char-traits-char-struct.md)|A struct that is a specialization of the template struct `char_traits`\<CharType> to an element of type `char`.|  
|[char_traits<wchar_t> Struct](../standard-library/char-traits-wchar-t-struct.md)|A struct that is a specialization of the template struct `char_traits`\<CharType> to an element of type `wchar_t`.|  
|[char_traits<char16_t> Struct](../standard-library/char-traits-char16-t-struct.md)|A struct that is a specialization of the template struct `char_traits`\<CharType> to an element of type `char16_t`.|  
|[char_traits<char32_t> Struct](../standard-library/char-traits-char32-t-struct.md)|A struct that is a specialization of the template struct `char_traits`\<CharType> to an element of type `char32_t`.|  
  
## Requirements  
  
- **Header:** \<string>  
  
- **Namespace:** std  
  
## See Also  
 [Header Files Reference](../standard-library/cpp-standard-library-header-files.md)   
 [Thread Safety in the C++ Standard Library](../standard-library/thread-safety-in-the-cpp-standard-library.md)