---
title: "Mutable Data Members (C++) | Microsoft Docs"
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ms.date: "11/04/2016"
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dev_langs: ["C++"]
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---
# Mutable Data Members (C++)
This keyword can only be applied to non-static and non-const data members of a class. If a data member is declared `mutable`, then it is legal to assign a value to this data member from a **const** member function.  
  
## Syntax  
  
```  
  
mutable member-variable-declaration;  
```  
  
## Remarks  
 For example, the following code will compile without error because `m_accessCount` has been declared to be `mutable`, and therefore can be modified by `GetFlag` even though `GetFlag` is a const member function.  
  
```  
// mutable.cpp  
class X  
{  
public:  
   bool GetFlag() const  
   {  
      m_accessCount++;  
      return m_flag;  
   }  
private:  
   bool m_flag;  
   mutable int m_accessCount;  
};  
  
int main()  
{  
}  
```  
  
## See Also  
 [Keywords](../cpp/keywords-cpp.md)