Compact Disk Read Only Memory (CD-ROM) is a compact disc that contains data accessible by a computer. While the compact disk format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data.
CD-ROMs are popularly used to distribute computer software, including games and multimedia applications, through any data can be stored (up to the capacity limit of a disc).
Some CDs hold both computer data and audio with the letter capable of being played on a CD player, whilst data (such as software or digital video) is only usable on a computer. These are called enhanced CDs. Although many people use lowercase letters in this acronym, proper presentation is in all capital letters with a hyphen between CD and ROM. It is also debated whether the correct terminology is read-only memory or media. It is Generally Accepted that in technical terms, media is the correct terminology.
However, due to the widespread use of ROM to refer to other devices such as EEPROM and Flash-ROM (where memory is the correct terminology) most people define CD-ROM as also being memory as it sounds like the abbreviation is from the same origin.
A hard disk (commonly known as a HDD (hard disk drive) or hard drive and formerly known as a fixed disk) is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces.
Strictly speaking "drive" refers to an entire unit containing multiple platters, a read/write head assembly, driver electronics, and motor while "hard disk" (sometime "platter") refers to the storage medium itself. hard disks were originally developed for use with computers.
In the 21st century, applications for hard disks have expanded beyond computers to include digital video recorders, digital audio players, personal digital assistants (PDAs), and digital cameras.
In 2005, the first mobile phone to include hard disk were introduced by Samsung group and Nokia.
The need for large-scale, reliable storage, independent of a particular device, led to the introduction of configuration such as RAID, hardware such as network attached storage (NAS) devices, and Systems such as Storage Area networks (SANs) for efficient access to large volumes of data.
A floppy disk is a storage medium, consists of a thin and flexible magnetic disk inside a plastic carrier.
A floppy disk drive or FDD or floppy drive, is a device used to read data storage information.
Floppies don't have much storage capacity.
Floppies can get affected by heat.
They have to handle more carefully.
Pen drives are robust and scratch free, thus ensuring maximum security for your data as compared to other traditional means of data storage.
Many available PC software suits permit the launch of an operating system from the Bootable pen drive. Moreover, companies selling pen drives nowadays also couple it with other devices like MP3 player, LED's or Swiss knife etc.