How to initialize a static member in a class in C
Oct 15, 2025 am 02:31 AM
Static members belong to classes rather than objects and need to be initialized outside the class. Use the static keyword when declaring, and initialize it in the global scope outside the class in the form of "class name::variable name=value" when defining, and access it through the class name and scope operator.
In C , a static member belongs to the class rather than any specific object. This means all instances of the class share the same static member. To properly initialize a static member, you must define and initialize it outside the class definition.
Declare the static member inside the class
Inside the class, you only declare the static member using the static keyword. No memory is allocated at this point.
class MyClass {
public:
static int count; // Declaration only
};
Define and initialize the static member outside the class
You must provide a definition outside the class, typically in a source (.cpp) file. This is where memory is allocated and the variable can be initialized.
int MyClass::count = 0; // Definition and initialization
This line should appear at global scope, not inside any function. If you're using header-only classes (eg, templates), you might place both declaration and definition in the header, but ensure there's only one definition across translation units.
Accessing the static member
You can access the static member using the class name and the scope resolution operator, without creating an object:
MyClass::count = 5; std::cout
Or through an instance, though this can be misleading:
MyClass obj; obj.count = 10; // Still refers to the same shared variable
For const integral or enum types, you can sometimes initialize inside the class:
class MyClass {
public:
static const int value = 42; // Allowed for const integral types
};
But even then, you may still need a definition in a .cpp file if you take its address.
Basically, declare it inside, define and initialize it outside — that's how static members work in C .
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