How to create a static variable in C
Sep 19, 2025 am 05:24 AM
A static variable in C retains its value between function calls and is initialized once. 2. Inside a function, it preserves state across calls, such as counting iterations. 3. In a class, it is shared among all instances and must be defined outside the class to avoid linking errors. 4. Static variables persist for the program’s lifetime, enabling data sharing without globals.
A static variable in C retains its value between function calls and is initialized only once. It can be created inside a function or at class level, depending on the context. Here's how to use it in different scenarios.
Static Variable Inside a Function
When declared inside a function, a static variable keeps its value across multiple calls to that function. It's initialized only the first time the function runs.
- Use the static keyword before the data type when declaring the variable inside the function.
- The variable is created and initialized the first time control passes through its declaration.
Example:
void counter() {
static int count = 0;
count ;
std::cout << "Count: " << count << std::endl;
}
Each call to counter() will increment count, preserving its previous value.
Static Variable in a Class
A static member variable belongs to the class itself, not to any specific object. All instances of the class share the same static variable.
- Declare the static variable inside the class using the static keyword.
- Define (and optionally initialize) it outside the class, usually in a source (.cpp) file.
Example:
class MyClass {
public:
static int value;
};
// Definition outside class
int MyClass::value = 0;
Now MyClass::value can be accessed without creating an object: MyClass::value = 5;.
Key Points
Static variables have a single storage location and persist for the lifetime of the program. They're useful for counting function calls, sharing data across objects, or maintaining state without globals. Remember to define static class members outside the class to avoid linking errors.
Basically just use static where needed and define class-level ones in a .cpp file. Doesn't take much but makes a big difference in behavior.
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