What is the difference between static binding and run time binding?

Answer 1

Static binding is where the linker copies the referenced module into the executable image of the program at compilation/link time. The referenced module becomes a part of the executable image. Dynamic binding is where the linker copies only a stub code for the referenced module into the executable image. That stub code loads the referenced module into memory at load/run time. Advantage of static is simplicity. The executable is stand-alone. Disadvantage is the executable image is larger, and if the referenced module changes, then each executable that uses it must be relinked. Another disadvantage is that if you have more than one executable using the module at the same time, you must have multiple copies of it in memory. Advantage of dynamic is reduced size of the executable image and that changing the referenced module does not require relink of the executable. Another advantage is that most operating systems can share the referenced module, meaning that only one copy of the referenced module need exist in all of memory for any number of references to that module, such as from multiple instances of the executable. Disadvantage of dynamic is that the executable is dependent on the shared library at run time. Another disadvantage is that, since the module is shared, it must be reentrant and thread safe, and this is not always done correctly.

Answer 2

Dynamic Binding or Late Binding

Dynamic Binding refers to the case where compiler is not able to resolve the call and the binding is done at runtime only. Let's try to understand this. Suppose we have a class named 'SuperClass' and another class named 'SubClass' extends it. Now a 'SuperClass' reference can be assigned to an object of the type 'SubClass' as well. If we have a method (say 'someMethod()') in the 'SuperClass' which we override in the 'SubClass' then a call of that method on a 'SuperClass' reference can only be resolved at runtime as the compiler can't be sure of what type of object this reference would be pointing to at runtime.

Static Binding or Early Binding

If the compiler can resolve the binding at the compile time only then such a binding is called Static Binding or Early Binding. All the instance method calls are always resolved at runtime, but all the static method calls are resolved at compile time itself and hence we have static binding for static method calls. Because static methods are class methods and hence they can be accessed using the class name itself (in fact they are encourgaed to be used using their corresponding class names only and not by using the object references) and therefore access to them is required to be resolved during compile time only using the compile time type information. That's the reason why static methods can not actually be overriden.

Answer 3

The answer relates to how C++ (and C#) decides which particular function is being referred when a call is made.

Static (or early) binding is considered the traditional method because it most closely resembles the behavior of C and other older programming languages. This is most often seen in cases of function overloading: when one function name can be differentiated based on its parameters and/or return types. In a static bind, the decision is made at compile time. Based on the parameters passed and return expected, the compiler decides on a match for the call and sets the call to the appropriate version of the overloaded function. If a match cannot be made, the compiler returns an error indicating that no such overload exists (given enough verbosity, the compiler will usually attempt to describe the specific form of the function it was attempting to match).

Dynamic (or late or run-time) binding, as the name implies, only occurs while the program is executing. It is considered a key aspect of object-oriented languages because it contributes to polymorphism. True OO languages onlyallow for dynamic binding; C++ and C# allow for both. In C++ and C#, a dynamic bind usually occurs with virtual functions: member functions belonging to a base class that can be redefined in a derived class.

Here is the reason for the distinction. When class definitions are compiled, part of the process involves the assignment of addresses to member functions. An overridden member function of a derived class will have a different address than the same member belonging to the base class. If a pointer is declared belonging to the base class, but the pointer is then initialized (with the new keyword) as an instance of the derived class, then it becomes necessary to reset the member function's address, at run-time, to point to that of the derived class instead. The virtual keyword clues the compiler to this need by setting up the necessary mechanisms to allow for the reset to take place at run-time; otherwise, it will default to pointing to the member of the base class. In C#, the additional override keyword is used to specifically point to a derived function overriding the base function.

Answer 4

When the method call is resolved at compile time, it is called as static binding,

when the method call is resolved at run time then it is called as dynamic binding.

In method overriding, the overridden method call is resolved using dynamic method dispatch(i.e it is resolved at run time).

Answer 5

Dynamic binding is implemented in java using dynamic method dispatch.

Dynamic method dispatch means the method of the class will be called whose object is created.For example:

class Animal

{

pulic void eat()

{

}

}

class Cat extends Animal

{

pulic void eat()

{

}

}

public class A()

{

public static void main(String ar[])

{

Animal a = new Cat();

a.eat();

}

}

Since in the above example object of the child class is created,so eat() of child class is invoked.

Answer 6

Static binding applies to basically all c function calls.

Dynamic binding applies to calls to function pointers.

Answer 7

static binding done at compile time where as dynamic binding done at run time. Dynamic binding is also called as Dyanamic method dispatcher.