>Could you estimate what percentage of time this is a concern in higher-level language like VB or VFP? Or, rather - could you give an example where it's pertenant to be aware of an ID/handle and their respective distictions and estimate how often that example is of concern?
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InVB, lots - dealing with printers, the VB developer references the device via an hDC - a handle to a device context. Want to get a control to do something? Send it a message using SendMessage() or PostMessage(); you just need the hWnd of the control. Want to check the completion status of a program you fired up to run in the background? If you have an hProcess (process handle) you can call GetExitCodeProcess(), or given the ProcessID, you can get a handle granting you all sorts of capabilities using OpenProcess().

I'd guess that my code contains lots of calls to the API layer that many others don't use. I can certainly write an app without resorting to talking to the API, but I can write a better one if I just ask Windows to do the tough stuff for me. You don't have to buy a lawnmower to keep your grass clipped; a herd of cattle will handle the task quite well.