Features of desktop MEMORY:The data written into RAM (read and write memory, namely memory bar) will completely disappear after power off. The earliest program data read into the CPU to execute comes from ROM (read-only memory) when the computer starts up. Memory is a computer (including SCM), the basic components, from the day there is a computer memory. And the external storage belongs to the computer peripheral equipment, the hard disk is after the development of magnetic tape, floppy disk after the production of external storage.