Data Storage in Computers

Data Storage in Computers – Notes

1. Introduction

• A computer cannot work on its own.
• We must give data and instructions to the computer to make it work.
• The computer processes the data using the CPU (Central Processing Unit) and produces information as output.

2. Data and Information

Data

• Data is a collection of unorganized facts and figures such as numbers, alphabets or symbols.
• Example: Marks of a student in 5 subjects.

Information

• Information is processed data that has meaning.
• Example: Percentage calculated from marks.

Relationship

• Data → Processing (CPU) → Information
• Input devices enter data → CPU processes → Output devices show information.

3. Units for Measuring Computer Memory

Computers store data in binary language (0 and 1).

Bit

• Smallest unit of memory
• Bit means Binary Digit

Byte

• 1 Byte = 8 Bits
• Larger Units of Memory

4. Types of Memory

Computer memory is divided into two main types:

1. Primary Memory (Internal Memory)

• Also called Main Memory
• Directly connected to CPU
• Stores instructions while the computer is working.

Types of Primary Memory:

RAM (Random Access Memory)

• Temporary memory
• Data is lost when the computer is turned off
• Called volatile memory

ROM (Read Only Memory)

• Permanent memory
• Data is not lost when power is off
• Called non-volatile memory

Types of ROM

1. PROM – Data can be written only once
2. EPROM – Can be erased using ultraviolet light
3. EEPROM – Can be erased using electrical signals

5. Secondary Memory (External Memory)

• Also called Secondary Storage
• Used to store large amounts of data permanently
• Not directly accessed by CPU
• Examples: Hard Disk, CD, DVD, Pen Drive, Memory Card

6. Storage Devices

Hard Disk

• Circular magnetic disk
• Very large storage capacity (up to 1 TB or more)
• Fast data access

CD (Compact Disc)

• Used to store audio, video and data

Types:

• CD-R → data written once
• CD-RW → data erased and rewritten many times

DVD (Digital Versatile Disc)

• Stores more data than CD
• Capacity up to 17 GB

Blu-ray Disc

• Stores 10 times more data than DVD
• Used for high-quality movies and games

Pen Drive

• Also called USB Flash Drive
• Small and portable
• Used to transfer files between computers

Memory Card

• Small storage device used in phones, cameras and tablets

7. Difference between Primary and Secondary Memory

Exercise Solutions

A. Tick (✓) the correct answer:

1. Name the CD on which data can be erased and rewritten many times.

Answer: (c) CD-RW

2. 1 Terabyte is equal to

Answer: (a) 1024 GB

3. The smallest unit of computer memory is called

Answer: (b) Bit

4. Which of the following is a feature of ROM?

Answer: (c) ROM stores a special software called BIOS

5. Which storage device can store and transfer data from one computer to another?

Answer: (d) All of these

B. Fill in the blanks:

1. Primary memory is called internal memory.

2. Four bits make a Nibble.

3. Pen drives have become very popular these days.

4. Hard disk is the largest storage device on the computer.

5. Secondary memory is always non-volatile in nature.

C. Write T (True) or F (False):

1. Computer understands binary language.    T

2. Data is stored in the forms of bits.    T

3. Secondary memory is classified into RAM and ROM.    F

4. One Gigabyte is equal to 1024 Gigabytes.    F

5. ROM is a non-volatile memory.    T

D. Match the following:

Answer the Following Questions

1. What do you mean by data and information?

Ans: Data are unorganized facts and figures such as numbers or symbols.

Information is processed data that has meaning.

2. How is memory classified into different types?

Ans: Computer memory is classified into two types:

1. Primary Memory (RAM and ROM)

2. Secondary Memory (Hard disk, CD, DVD, Pen drive)

3. What is a hard disk?

Ans: A hard disk is a storage device that stores large amounts of data permanently inside the computer.

4. Differentiate between RAM and ROM.

Ans:                RAM                         ROM

• Temporary memory               Permanent memory
• Data lost when power off      Data not lost
• Volatile                                   Non-volatile

5. What do you mean by secondary storage?

Ans: Secondary storage is memory used to store large amounts of data permanently such as hard disks, CDs, DVDs and pen drives.