Difference between Function, Copy of Action & Externel Action

What is the diffrence between Copy of Action & Externel Action in QTP?
What is the diffrence between Function & Action?

[B]Question asked by visitor Gopalreddy[/b]

[B]What is the difference between an Action and a function?[/B]

Action is a thing specific to QTP while functions are a generic thing which is a feature of VB Scripting. Action can have a object repository associated with it while a function can't. A function is just lines of code with some/none parameters and a single return value while an action can have more than one output parameters.

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suresh