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> **Possible Duplicate:**  
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> [Is CLR loaded and initialized everytime,when a new managed application is loaded ?](https://stackoverflow.com/questions/3245791/is-clr-loaded-and-initialized-everytime-when-a-new-managed-application-is-loaded) 
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When you startup some .NET app, does the OS have to load the .NET runtime each time too or is that already running? 

The app has to be JIT'ed before it can be executed each time by the runtime right?

Doesn't that slow things down? How does this work?