Hard Drives, floppies, CD drivers, CDR & CDRW, Tape Drives, Zip and Jaz Drives

NOTE:  you will need to have read the Bits and Bytes section, in order to fully understand this section.

We've all heard the words . . . disk drive, hard drive, memory, diskette, CDR, CDR/W, tape backup, etc.  There is often confusion between storage and memory, so let's start by clearing that up :

• Storage is long-term holding of bits, through the use of hard drives, diskettes, write-able CD's, and tape drives.  Storage is slow, at least compared with memory.  For comparison, bits are retreived in about 8-10 ms (one ms, or millisecond, is 1/1000th of a second), with a fast hard drive.  Storage is cheap, and huge . . . thousands of Megabytes (or MB, where 1024 MB = 1 GB, or Gigabyte) are stored on a single hard drive.  When you turn your PC off all info stored in storage remains and is saved !!

• Memory is short-term holding of bits through the use of chips, mounted on the motherboard.  Memory is fast - bits are retrieved in the ns rage (ns is "nanoseconds", or 1/1 millionth of a second).  Actually, most moderns memory chips are rated from 60-70 ns.  Memory is expensive, and therefore usually holds small amounts of data.  Today's PC's generally have just 64-128 MB (Mega-bytes, where 1 MB = 1024 k Bytes) of memory.  When you turn your PC off all data residing in Memory is cleared - gone !!

Storage vs Memory

Drives are slow but cheap, memory is fast but expensive.  If hard drives were fast enough, there would be no need for memory.  Conversely, if memory was cheap enough, there would be no need for storage.  Due to the limitations of each, they use a hybrid solution, and include both.  In fact, there are actually several types of memory used, which we will describe shortly.