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Read Only Memory (ROM)
Digital Versatile Disc or Digital Video Disc (DVD)
ROM is the permanent memory, i.e., it holds the data even if the system DVD is almost similar to a CD. The only difference is that it can hold more
is switched off. It holds the starting instructions that are required to information than a CD. DVDs are widely used for storing and viewing movies
start a computer. It is also called non-volatile memory.
and other data. Just like CD drives, the DVD drive reads information stored
Secondary Memory DVD on a DVD. A DVD can hold 4.7 GB to 17 GB of data.
This memory is permanent in nature and is not directly accessed by the CPU. It allows users to Blu-ray Disc
store data that may be easily retrieved.
Blu-ray disc is an optical disc. It is used for storing a large amount of data. The
Secondary memory devices are also called secondary storage devices. Lets learn about some main difference between DVDs and Blu-ray discs is that storage capacity of
secondary storage devices. Blue-ray disc is higher than that of the DVD. A Blu-ray disc can hold 25GB to
50GB data. Blu-Ray disc
Hard Disk
Pen Drive
Hard disk is permanently fixed in the CPU Box. The most important
function of the hard disk is to store program files and data files. Pen drive is a portable storage device and is easy to use as it is small and
Hard disk can be carried in a pocket and plugged into any computer with a USB
Pen drive drive. Pen drive has storage capacity of upto 1TB.
Factbot
Memory Card
World's first hard disk was introduced by IBM in 1956.
Memory card is commonly known as multimedia memory card. It is very small
in size usually 1-1.5 inches. These are used in smart phones and digital cameras.
Hard disks are available in a variety of sizes with storage You need to have a card reader to read/write the data on a memory card.
capacities as high as 5 TB (Terabyte) or even more. The CPU can Memory card
access data stored on a hard disk much faster than it can access
data on a CD. Double Tap 21 st #Technology Literacy
Century
Skills
External hard disks are also available. They are the hard disks that External hard disk Fill in the blanks.
can be connected to any computer with the help of a USB port. 1. The storage space in a computer is called .
Compact Disc (CD) 2. ROM is the memory.
Compact disc (CD) is an external storage device. It can hold upto 700 MB 3. is a portable storage device.
of data. To be able to write data on or read data from a CD, you need a
component called a CD drive. The CD drive reads information stored on a MEASURING THE COMPUTER’S MEMORY
compact disc. CD drive is usually connected inside the CPU box but can CD The basic unit for measuring the memory of a computer is byte. A byte consists of a group of
also be connected using a USB port. eight bits, for example, 10001011, i.e. 1 byte equals to 8 bits. A group of 4 bits is known as a
nibble (half byte), for example, 1001, i.e. 1 nibble equals to 4 bits. Other units for measuring
the computer’s memory are kilobyte, megabyte, gigabyte, terabyte, and so on.
1024 bytes = 1 Kilobyte (KB)
1024 KB = 1 Megabyte (MB)
1024 MB = 1 Gigabyte (GB)
CD Drive
#Data Storage and Memory 13

