Data Structures and Algorithms with Object-Oriented Design Patterns in C++

Variables, Pointers and References

A variable is a programming language abstraction that represents a storage location. A variable has the following attributes:

name: The name of a variable is the label used to identify a variable in the text of a program.
address: The address of a variable is the memory address of the storage location(s) occupied by that variable. The address attribute of a variable is also known as the l-value because the l-value of a variable is required when a variable name is used on the left side of an assignment statement.
size: The size of a variable is the amount of storage (in bytes) occupied by that variable.
type: The type of a variable determines the set of values that the variable can have and the set of operations that can be performed on that variable.
value: The value of a variable is the content of the memory location(s) occupied by that variable. (How the contents of the memory locations are interpreted is determined by the type of the variable). The value attribute of a variable is also known as the r-value because the r-value of a variable is required when a variable name is used on the right side of an assignment statement.
lifetime: The lifetime of a variable is the interval of time in the execution of a program during which a variable is said to exist. Some variables exist for the entire execution of a program; some are created and destroyed automatically during the execution of a program; and others are explicitly created and destroyed by the programmer.
scope: The scope of a variable is the range of statements in the text of a program in which that variable can be referenced.

Consider the C++ variable declaration statement:

int i = 57;

This statement defines a variable and binds various attributes with that variable. The name of the variable is i, the type of the variable is int, its size is

(typically two or four bytes), and its initial value is 57.

Some attributes of a variable, such its name, type and size, are bound at compile time. This is called static binding. Other attributes of a variable, such as its address and value, may be bound at run time. This is called dynamic binding.