When you use a user defined operator, (eg multiplication on a vector structure), does the compiler place a call to the operator ''function'' (Slow)? Does it actually place the operator code in with the rest of the code (so you have one copy of the operator code per use of the operator? - Fast), or does it do something in between, like a Jump? At the moment I use macros for all vertex and matrix structure operations, but they''re a lot uglier and more difficult than operators. Yet speed is very important. (I''m using Visual C++ 6.0 if that makes a difference) Secondly, the register keyword: if you don''t use it, does the compiler decide to place in registers whatever variables it thinks best, or does it not use register variable storage and use stack/ram storage instead?. Thirdly, can you stuff your program up by using the register keyword - eg if you have a register variable and you want a pointer to it. (Pointers to registers don''t exist, right?) Thanks for any assistance Simon Hill

Overloaded operators are functions. However, like all functions, they can be inlined. When they are inlined, they have all the speed advantages of macros.