Storage Device

 

                                            Chapter 3

          

Lesson Overview

Human beings store the information in their mind (memory of humans). Likewise, computer store information in its primary and secondary memory (memory of computer). They both can recognize it in the time of need. The physical parts of a computer that stores information and data either permanently or temporarily are called storage devices. They are classified as removable and non-removable storage devices.

Computer memory is divided in to two parts. They are:

1.   Primary Memory

2.   Secondary Memory

Primary Memory

The memory that stores both processed and unprocessed data, program and instructions is known as primary memory. It is necessary for a computer to work. It is the main area where the data is stored. It operates at a very high speed. The stored data can be recalled and processed by the CPU. There are two types of primary memory. They are:

1.   Random Access Memory

2.   Read Only Memory

 

Random Access Memory

It is a primary or internal memory in a computer that stores data and programs temporarily which are currently being used. Its contents can be directly accessed and customized by the CPU directly. RAM stores data temporarily. When you switch off the computer, all the contents of RAM get erased. Due to this reason, RAM is also known as volatile memory. It can be also categorized as Static RAM and Dynamic RAM.

 

Read Only Memory

It is called as Read Only Memory because you can only read information but cannot modify it. It is the built-in memory of computers. The user cannot write into a ROM. Its contents are written at the manufacturing time. It stores data permanently. When you switch off, the contents of ROM do not get erased. So, it is also known as non-volatile memory. They are of three types. They are Programmable ROM, Erasable Programmable ROM and Electrically Erasable Programmable ROM.

Secondary Memory

The memory that stores data and information are stored on a long-term basis is called as secondary memory. It is needed in computers to store large amount of data and programs for future use. It is a non-volatile memory. There are many popular secondary devices.

Some of them are given below:-

           i            Hard Disk

        ii            Optical Disc

    iii            Pen drive

Hard Disk is a commonly used secondary storage device that stores nearly 20 MB -2 TB or more amounts of data, information and programs permanently. It is made up of collection discs (one below another) called platters in which data is stored/ recorded. The container of hard disc includes the motor for rotating the disc. Hard disc generally offer more storage and quick access to data. Hard disk rotates while recording (3600-7200 per second), it is measured in the unit RPM.

 

Optical disc is a glass or plastic coated with reflecting medium. It is portable and can hold large amount of data. It is generally used for storing music, movies and software programs. Compact, Lightweight, durable and digital are the advantages of it. It can store nearly 650 megabytes (MB) or more amount of data.

 

Here are some types of optical disc:-

S. N	Types of Optical Disc	Definition
1	CD-ROM	It stands for Compact Disc Read Only Memory which stores wide variety of information. It is mainly used for recording music. It can store up to 700 MB.
2	CD-R	CD-R stands for CD-Recordable. You can only write data once to read later. The data cannot be erased after it is written.
3	CD-RW	It stands for CD-Rewritable. You can change/modify the data after it is written. It is also known as Erasable-CD.
4	DVD	It stands for digital versatile disc that can store a very large amount of data. It works similar to compact disc. It can store 4 GB to 17 GB of data. They are used to store large multimedia presentations and movies.
5	Blu-ray	Blu-ray is an optical disc format designed to display high definition video and store large amounts of data.

 

Pen drive is a small, lightweight, removable disc. It is also known as flash disc or USB. We can read, write, copy, delete and move data from computer to pen drive or pen drive to computer. It comes in various capacities like 2 GB, 4 GB, 1 TB, etc. We can easily carry it from one place to another. It is plugged into computer's USB port and computer automatically detects this device. And now, you can transfer files, data, program, etc. from computer to pen drive or pen drive to computer.

 

1.    Write true and false:

a.   1 bit is equal to 1 nibble.

b.   Hard disc does not contain any motor for rotating.

c.    There are three types of primary memory.

d.  CD-ROM is commonly used for storing music.

e.    Flash disk cannot be carried from one place to another.

f.     1024 GB is equal to 1 TB.

 

2.   Answer in one word:

a.   What is the full form of CD-ROM?

b.   Which device works similar to compact disc?

c.    What is the full form of USB?

d.  What is the unit to measure the rotating speed of Hard Disc?

e.    What are the two types of RAM?

f.     The physical parts of computer that stores information and data either permanently or temporarily.

g.   It needs to be plugged in computer's USB port to transfer files.

h.   Smallest and largest unit of memory.

i.      Name the types of RAM.

j.       The memory that stores both processed and unprocessed data.

 

3.   Answer these questions.

a.   What are the differences between primary memory and secondary memory?

b.   What are RAM and ROM? Why is RAM caked as volatile memory?

c.    Define hard disc and how is it made.

d.  Write the different units of memory.

e.    Write the advantages of flash disc.

f.     Write short note on optical disc.