Page 65 - Computer

devices. USB flash drives have proved Optical discs
to be the best rewritable storage media Optical discs are storage media that
among the public due to the common use lasers to read and write data. The
availability of USB ports built into most most common types of optical discs are Computer Science

models of personal computers. Figure CDs (Compact Discs), DVDs (Digital
FOR ONLINE READING ONLY
3.28 (a) and (b) shows the inside and Versatile Discs), and Blu-ray discs.
outside of USB flash disk. Optical drives are commonly found in
desktop and laptop computers. They are
also found in some gaming consoles and
home entertainment systems.

Compact Disc
A Compact Disc (CD) (see Figure 3.30) is
a type of optical disc that is smaller than
a hard disc. It uses laser beam technology
(a) Inside view of (b) Top view of USB to read and write data. CD drives can
USB flash disk flash disk store 650 - 700 MB of data on one side of
a CD. There are three basic types of CD:
Figure 3.28: USB flash disk CD-ROM, CD-R, and CD-RW:
(i) Compact Disc- Read Only

Memory cards Memory (CD-ROM) is like a
Memory cards are used in many commercial music CD. Read-
electronic devices, including digital only means the user cannot write
or erase its content,
cameras, mobile phones, laptops, MP3
players, and video game consoles. They (ii) CD-R (CD-Recordable) can be
written only once and read many
are small, re-recordable, and able to times but cannot be rewritten or
retain data without power. Figure 3.29 erased,
shows some examples of memory cards. (iii) Compact Disc-Re-Writable
Memory cards are like flash disks in (CDRW) can be rewritten or
terms of speed and reliability, except erased multiple times.
they are much smaller.

Figure 3.29: Sample of a memory card
Figure 3.30: Compact Disc
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