HARD DISK
When you save data or install programs on your computer, the information is
typically written to your hard disk. The hard disk is a spindle of magnetic
disks, called platters, that record and store information. Because the data is
stored magnetically, information recorded to the hard disk remains intact after
you turn your computer off. This is an important distinction between the hard
disk and RAM, or memory, which is reset when the computer's power is turned
off.
The hard disk is housed inside the hard drive, which
reads and writes data to the disk. The hard drive also transmits data back and
forth between the CPU and the disk. When you save data on your hard disk, the
hard drive has to write thousands, if not millions, of ones and zeros to the hard
disk. It is an amazing process to think about, but may also be a good incentive
to keep a backup of your data.