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• Compact Disc (CD): CD or Compact Disc is a digital optical disc used for storing data. It is
made up of light weight plastic material with a chemical coating on one side where data is
stored.
It is inserted into a CD/DVD drive or CD/DVD writer of a CPU. In CD ROM (Compact Disc Read
Only Memory) data can only be read whereas in CD writer, data can be read and written as
well. The storage capacity of 120 mm standard CD is 700 MB.
Types of CDs:
◦ CD-ROM (Compact Disc Read Only Memory): A CD-ROM is a CD that
contains data that was written when the CD was manufactured. The data
cannot be modified or erased.
◦ CD-R (Compact Disc Recordable): A CD-R can be used to write data by the
user only once. This data cannot be changed or erased.
◦ CD-RW (Compact Disc Rewritable): A CD-RW can be used to write data again and again.
The data can be erased and modified as many times as required.
• Digital Versatile or Video Disc (DVD): DVD or Digital Versatile/Video Disc is
an optical disc which looks like a CD but has a capacity to store data up to 17.1
GB. To read information stored in a DVD, it has to be inserted into a DVD ROM
or DVD Writer or DVD player (to copy information on a DVD, one has to use a
DVD writer).
• Blu-Ray Disc: A Blu-ray Disc can store up to 128 GB of data. It was developed
by the Blu-ray Disc Association (BDA). It is much advanced than CDs or DVDs.
Blue violet laser is used to read or write data on a Blu-ray disc.
• Flash Drive: A Flash Drive is a small portable data storage device integrated with a Universal
Serial Bus (USB ) connector.
◦ Pen Drive: It is small in size, handy and is a detachable device from which
data can be read, copied or transferred from one system to another. It is
re-writable and weighs less than 25 gm.
Nowadays, pen drives are the most commonly used external storage and data transferring
device. It has an attachment slot which can be easily inserted or attached into the
computer’s USB port.
◦ Memory Card: It is commonly known as a multimedia memory card. It is
very small in size, usually 1–1.5 inches. These are used in mobile phones and
digital cameras. You need to have a card reader to read stored data on a
memory card.
• Solid State Drive: It is a storage device that uses flash memory to store data, offering faster
access speeds than traditional hard disk. Unlike HDDs, SSDs have no moving parts, making
them more durable, quieter, and quicker in terms of data retrieval and boot times. SSDs are
commonly used in modern computers and laptops for improved performance.
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Computer—Hardware Components

