Bits
and Bytes
RAM and ROM
Storage Devices
Drives
Capacity
All data and instructions inside a computer are stored and processed as numbers.
The computer understands two numbers. Zero 0 and One 1.
These are binary digits called Bits for short. 
So a bit is 0 or 1 .
Computer data is stored in a series of eight bits known as Bytes.
So 00110011 is a byte and 10101010 is also a byte.
ROM: stands for Read Only Memory. This memory is permanent. It cannot be changed. ROM keeps it memory even after the computer is turned off.
RAM: stands for Random Access Memory. This memory
is temporary. It can change. RAM stores data and instructions while the
computer is turned on. When the computer is turned off all the data stored in ROM is
lost unless saved. Extra RAM can be bought and installed in the computer. Here is a
RAM chip 
| Floppy Disk | CD-ROM | ZIP Disk | Hard Disk |
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Floppy disks: are used to store information. You can put information on and take information off of a floppy disk.
Before using a floppy disk for the first time you should Format the
floppy disk.
Formatting the disk prepares it for use.
Be careful formatting also wipes all of the information
off of a Floppy Disk.
Hard disks: are usually located inside the computer. They can store huge amounts of information. Data can be put on and taken off of a Hard disk. The Hard disk stores the operating system, programs, and most other files that you have saved onto your computer.
CD-Rom: data is transferred to a CD before it is sold and cannot be changed by the user.
CD-R: these have become very popular. If you have a CD Writer on your computer you can create CD's. Once created the information cannot be removed. Data and music files can be saved onto a CD-R.
CD-RW: these are similar to CD-R. If you have a CD Writer on your computer you can create CD's. The only difference between a CD-R and a CD-RW is that you can rerecord as many times as you wish if using a CD-RW. CD-RW however is more expensive to buy than a CD-R.
ZIP disks can also store a lot of information.
Drives: Disks are inserted into the appropriate disk drives. You will have inserted a floppy disk into the floppy disk drive in a machine. A CD is inserted into the CD-ROM drive in a machine. Once inserted a Disk Drive spins the disk while read/write heads read or write data onto the disk.
Capacity: The amount of data that can be stored in memory or on a disk is called its capacity.
The capacity of a Floppy Disk is 1.44 MB. MB stands for Mega Bytes.
The capacity of a CD-ROM is usually 650-700 MB.
The capacity of a Hard Drive can vary. You can purchase many different sizes for example 2GB, 6GB, 10GB and 20GB. Gb stands for Giga Bytes.
To find out how a hard disk works click here to go to the How Stuff Works website.
Copyright © Catherine O'Sullivan, 2001