February 13, 2011

 CD-ROM

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CD-ROM stands for Compact Disk Read Only Memory is a type of secondary storage or optical disc that users can read only but not write or erase. Philips and Sony companies invented Compact Disc in year 1982. CD-Rom is a WORM (Write Once Read Many times) device.  Typically they can store up to 600-700 MB of data or 70 minutes of audio, also store video, data, and text. The diameter of a Compact Disk is 4.7 inches and its thickness is 0.047 inches. A single Compact Disk equal to : 1500 - 5.25-inch floppy disks, 450 - 3.5 inch floppy disks and 274,000 pages of text.


Types of Compact Disks :

(1)  CD-ROM     :  
Compact Disk Read Only Memory (Write Once Read Many times)

(2)  CD-R       :  
(Compact Disc-Recordable) WORM disks for Well known technology

(3)  CD-RW      :  
(Compact Disc-ReWritable) Rewritable and erasable.

(4)  CD Extra    :  
For Multimedia purpose. Developed by Sony, Philips and Microsoft.

(5)  CD-DA      :  
(Compact Disk Digital Audio) Audio CD, Digital Audio Developed by Philips and Sony companies.

(6)  Photo CD      :  
Developed by Kodak and Philips companies.

(7)  Video CD      :  
Can hold approximately 70 minutes of recorded video.

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January 5, 2011

 Hard Disk

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The Hard drive also called the hard disk or fixed disk. This is the main storage for a computer and Non-volatile storage device. Every computer has a hard disk they are used to store the data files. Computers store information in two locations, First one, the computer’s RAM is used as a temporary storage location since whatever it contains is lost when the computer is powered off and Second one, Information that is stored permanently is written to the hard drive. Hard disk/Hard drive is different from RAM, because the information stays stored even if the power is turned off. Hard Drive can store a large amount of computer data in a small space and it storage provides faster access to files than a diskette.

Hard disks contain a number of magnetic platters that store information in the form of 0’s & 1’s and is stored in a series of concentric circles. A hard disk consists of one (or) more platters and several read/write heads that read and record data magnetically on platters, a stack of rotating disks inside the hard drive.  A read/write head is the device that reads the data from the disk platter into the computer.


Types of HDD (Hard Disk Drives) :
1.    IDE : Integrated Drive Electronics. it also known as PATA drives ( Parallel Advance Technology Attachment )
2.    SATA : Serial ATA or Serial Advance Technology Attachment.
3.    SCSI : Small Computer System Interface.
4.    SAS : Serial Attached SCSI.


Types of Hard Disk interfaces:

HD drives come in two main sizes, (i) 2.5" for laptops and (ii) 3.5" for desktops.

•    Desktop Hard Disk Types :- 3.5', IDE and SATA Interfaces.
•    Laptop Hard Disk Types :- 2.5', 1.8', IDE, SATA, SCSI.
•    Server Hard Disk Types :- 3.5', SATA, SCSI.
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December 29, 2010

 Floppy Drive

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Floppy drives are most advanced storage devices and it reads and writes data on floppy disks. Floppy Drive connects to the motherboard with a ribbon (data) cable and also power cable attached to it. Presently new computers do not have this floppy drives because USB flash drives and optical drives have replaced floppy drives in newer systems, it can be added internally to your computer (or) externally with a USB cable. It is a removable media or removable drive you can remove whatever disk is currently in the drive, and replace with another.
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