Basic VM memory usage question

I've read a bunch of guides on VMware memory usage but still have a basic question.

I have a 8GB Linux host with a windows VM which has 4GB memory allocated. If I run up the VM, and run top on the Linux host, I see 4.0G has been allocated to it (RES shows 4.2g SHR shows 4.0G). This is before I open any programs in Windows.

So, does that mean that 4GB is not available to the Linux host as soon as the VM starts? I thought memory was only allocated when requested by the guest?

Thanks

Nick