difference

[chaisen2006]

what is the difference between a 'declaration','declaration proto-type' and 'defination'.

[caradoc]

When we have declared a variable, we have meant that we have told the compiler about the variable; i.e. its type and its name, as well as allocated a memory cell for the variable .
This latter action of the compiler, allocation of storage, is more properly called the definition of the variable. The stricter definition of declaration is simply to describe information about the variable.
The prototype declaration defines its interface--how the prototype communicates with the rest of the scene and what parameters may be set for each instance of the prototype.