There are two differences between a declaration and a definition: In the definition of a variable space is reserved for the variable and some initial value is given to it, whereas a declaration only identifies the type of the variable. Thus definition is the place where the variable is created or assigned storage, whereas declaration refers to places where the nature of the variable is stated but no storage is allocated. Secondly, redefinition is an error, whereas, redeclaration is not an error.
