STORAGE POWER OF A MODERN COMPUTERTECHNOLOGY

• Computer Storage
– Refers to the data stored in an electromagnetic form to be used by the processor
• Storage Capacity
– Is the number of characters that can be stored on a computer
Computer
Stores a variety of data and information in its memory 

Computer  Stores numbers (0-9), letters (A-Z) and symbols and other characters (#, {}, ‘, ~, ^) 
It uses the binary system to represent these characters
The 0s and 1s in the binary system are known as bits (binary digits)
A bit is the smallest unit of measurement of storage capacity
A set of eight bits is called a byte
Kilobytes, megabytes, gigabytes and terabytes are higher units for measuring the storage capacity of a computer 

8 bits = 1 byte
1024 bytes = 1 kilobyte (KB)
1024 KB = 1 megabyte (MB)
1024 MB = 1 gigabyte (GB)
1024 GB = 1 terabyte (TB)
Computers use two types of storage:
• Internal storage
• External storage
Internal Storage
It is one of the main components of the system unit
Also known as the main memory
Stores data and instructions on the computer
Stores the output data temporarily before it is sent to the output device  

It is volatile and its capacity is also limited
 The act of retrieving existing data from memory is called reading
 The process of storing data in memory is called writing
 There are two types of internal storage: • Random Access Memory (RAM)
• Read Only Memory (ROM)

External Storage
 It is a permanent storage area
 Stores data and programs that are not needed immediately by the computer
 Also known as secondary storage
 Data stored in this medium is permanent
 It is inexpensive and has a large storage capacity
 You need a storage device called a drive to write to and read from a storage medium
Some of the commonly used external storage devices are:
• Hard disk drives
• Floppy disk drives
• Compact Disk – Read Only Memory (CD-ROM) drives
• Digital Video Disk (DVD) drives
• CD and DVD writers
Hard Disk Drive:
• Is an external storage device used to store large quantities of data
• Is attached to the system unit from within
• Is packaged along with the hard disk


Hard Disk Drive:
• Is used to read data from and write data to the hard disk
• Has a storage capacity varying from 40 GB to 80 GB to a few terabytes
Floppy Disk Drive: 


• Is an external storage device used to read from and write to a floppy disk
• Is also called a floppy or diskette
• Is a portable storage medium that can store a small amount of data
• Has a storage capacity of 1.44 MB
• Is prone to damage by heat and dust
Compact Disk -Read Only Memory (CD-ROM) Drive
• Is used to read from a CD-ROM
CD-ROM:

• Is a storage medium
• Has a large storage capacity of 650 MB or 700 MB
• Is less prone to damage
• Is nowadays available as rewritable CD 


Rewritable CDs and CD Writers:
• Are storage devices that can write data to a CD
• Store a large amount of data on a CD, with a minimum range starting at 650 MB
• Can read CD-ROMs
Digital Video Disk (DVD) Drive:
• Is an external storage device
• Used to read from a DVD-ROM
DVD-ROM:

• Is similar to a CD-ROM

• Can store a minimum of 4.7 GB
• Can store up to 17 GB
Used to store multimedia objects that combine high quality sound and graphics
Remember this

• Bit
– Smallest unit of measurement of storage capacity
• Byte
– Set of eight bits
• CD-ROM
– Compact disk that cannot be overwritten
• CD-ROM drive
– External storage device used to read from CD-ROM
• CD writer
 

Storage device that can write data to rewritable CD
• Drive
– Storage device used to write to and read from storage medium
• DVD drive
– External storage device used to read from DVD-ROM
• External Storage

– Permanent storage area required to store data and programs that are not needed immediately by the computer
• Floppy disk
– Portable storage medium that can store a small amount of data
• Floppy disk drive
– External storage device used to read from and write to a floppy disk
• Hard disk drive


– External storage device attached to the system unit from within. A hard disk drive can be found in almost any PC.
• Primary storage
– Internal storage, or main memory of a computer. It contains data and instructions for processing. It also holds the output data temporarily before it is sent to an appropriate output device.
• RAM, Random Access Memory

– Storage area used for temporarily holding programs and data for processing.
• ROM, Read Only Memory
– Storage area used for holding instructions needed for starting a computer. These instructions cannot be erased or modified.
• Writing
– Process of storing data in memory. This process is also referred to as reading in.

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