dynamic binding

The property of object-oriented programming languages where

the code executed to perform a given operation is determined

at run time from the class of the operand(s) (the receiver

of the message). There may be several different classes of

objects which can receive a given message. An expression may

denote an object which may have more than one possible class

and that class can only be determined at run time. New

classes may be created that can receive a particular message,

without changing (or recompiling) the code which sends the

message. An class may be created that can receive any set of

existing messages.

C++ implements dynamic binding using "virtual memberfunctions".

One important reason for having dynamic binding is that it

provides a mechanism for selecting between alternatives which

is arguably more robust than explicit selection by

conditionals or pattern matching. When a new subclass is

added, or an existing subclass changes, the necessary

modifications are localised: you don't have incomplete

conditionals and broken patterns scattered all over the

program.

See overloading.