Why do some variables' names end in underscore?

Question

On Open Zeppelin's ERC20 BasicToken contract the variable totalSupply_ follows a naming convention I haven't seen before.

Is that to differentiate it from the function totalSupply() below or is there another reason?

Answer 1

Yes that is precisely why.

If totalSupply_ was named totalSupply it would clash with the function totalSupply() and you would get the following error message:

DeclarationError: Identifier already declared.