About Memory

I want to know difference between virtual memory, logical memory and physical memory?

basically when u talk about memory it is main memory in terms physical it is RAM.
to address the data on this physical memory two type of adressing is done.
One is direct addressing where exact adress is used. the second one is logical adressing. here the address is divided into two parts one is base address and the second one is offset address. this method is called logical addressing.

In order to handle this logical addressing a memory management unit (MMU) is present in the cpu.

Virtual Memory : - when main memory is not sufficient to handle all the programs then the processor uses a part of hard disk which if in case of Unix it is a special type of file system is used to accesses it faster. this is called virtual memory.

What is the difference between find .-name "*.properties" & find .-name "*.properties" | grep -i $home.