AHMEDABAD INTERNATIONAL SCHOOL

STUDY MATERIAL

Grade and Section 7 Subject: ICT

Chapter Name/Topic Storage Media

The computer memory is classified into two types- Primary memory and Secondary
memory.
Primary memory is also known as “main memory”or “internal memory” which is located
in the motherboard of a system, or as we say which is directly connected to the CPU.
It is the place where only a little bit of data is stored either by a manufacturer or by a user.
Primary memory holds only those data and instructions on which the computer is currently
working.
It is generally made up of semiconductor devices.
The primary memory is divided into two parts -
● RAM
● ROM
RAM:
● RAM is a form of data storage that can be accessed randomly at any time in any
order by CPU.
● RAM contents can be changed or altered as and when required.
● RAM allows the computer to read data quickly to run applications.
● RAM is volatile i.e its contents are lost when the device is powered off.
● Larger than ROM; can be up to some GigaBytes (GB)
ROM:
● ROM is also a form of data storage that generally stores hardware instructions for
the computer to start initially.
● ROM cannot be altered or reprogrammed.
● ROM stores the program required to initially boot the computer or reboot the
computer.
● It only allows reading.
● ROM is non-volatile i.e. its contents are retained even when the device is powered
off.
● Smaller but large enough to hold basic instructions; is up to some Mega Bytes (MBs)
Main Memory:
Main memory (sometimes known as internal memory or primary storage) is another name
for RAM and ROM.
Main memory is usually used to store data temporarily. In the case of RAM, it is volatile
(this means that when power is switched off all of the data in the memory disappears)
Main memory is used to store data while it is being processed by the CPU. Data can be put
into memory and read back from it very quickly.

Backing Storage or secondary storage

Backing storage (sometimes known as secondary storage) is the name for all other data
storage devices in a computer: hard-drive, etc
Backing storage is usually non-volatile, so it is generally used to store data for a long time

AIS/2024-25/GR-7/ICT/Study material/ Storage media

Accessing Stored Data:
A serial (or sequential) access storage device is one that stores files one-by-one in a
sequence.

A non-computer serial access device that will be familiar to you is a

VHS videotape. Because video is stored on a long piece of tape,
when TV shows are recorded onto the tape, they go on one-by-one,
in order...
If you want to watch a show that you recorded earlier, you have to
rewind / fast-forward through all other shows until you find it.

Direct / Random Access:

A direct (or ‘random’) access storage device is one that stores files so that they can be
instantly accessed; there is no need to search through other files to get to the one you want.
An example of a direct access device would be a DVD movie. Unlike the VHS videotape
movie, you can jump to any scene on a DVD.
All parts of the DVD are directly accessible. This type of file storage is called direct access

Magnetic storage
Definition: Magnetic storage is also known as “Magnetic Media” or “Magnetic Memory”
or “Magnetic Medium“
Magnetic storage media and devices store data in the form of tiny magnetised dots. These
dots are created, read and erased using magnetic fields created by very tiny electromagnets.

Fixed Hard Disks/Drives:

Available on all computers and is the main method used for data
storage
Uses a read/write head to write and read data from it
Disk surface coated in magnetic film; storage is done by altering binary
codes to 1s or 0s

USES
● Used to store operating systems and working data
● Used for storing application software
● Real time systems and online systems used fixed hard drives

Advantages Disadvantages
● Very fast data transfer rate and fast ● Can be easily damaged
access times to data ● They lack portability
● Have very large memory capacities

AIS/2024-25/GR-7/ICT/Study material/ Storage media

Portable Hard Drive

Like fixed hard disks but are usually connected via universal serial
bus(USB)
USES
● Can be used as backup systems to prevent loss of data
● Can be used to transfer data, files and software between
computers

Advantages Disadvantages
● Data access time and transfer rate is ● Can be easily damaged
very fast
● Large memory capacities
● Can be used to transfer information
between computers

Magnetic Tapes:

Magnetic tape is a large-capacity,

serial access medium. Because it is a
serial access medium, accessing
individual files on a tape is slow.
Tapes are used where large amounts
of data need to be stored, but where quick access to individual files is
not required. A typical use is for data back-up
USES
● Application where batch processing is used
● Used as a backup media

Advantages Disadvantages
● Generally, less expensive and very ● Access time is very slow
robust technology ● When updating another tape is
● Data transfer rate is fast needed

Optical Storage Devices

Optical storage devices save data as patterns of dots that can be read using light. A laser
beam is the usual light source.
CD ROM
Use:
CD-ROM disks are read-only. CD-ROMs are normally used to store:
● Audio CDs
● Software Applications
● Device Drivers

AIS/2024-25/GR-7/ICT/Study material/ Storage media

Advantages: Disadvantages

● Hold more data than floppy ● Data transfer rate is slower compared to
disks. other storage mediums.
● Cheaper than hard drives and ● Not robust; easily damaged or scratched.
USBs. ● Smaller storage capacity than a hard drive or
● Compatible with audio systems. DVD
● Small and portable ● Data transfer rate and data access time are
slower

DVD-ROM
Use:
DVD-ROMs disks are read-only. DVD-ROMs are normally used to store:
● DVD Movies
● Software Applications
● Computer Games

Advantages: Disadvantages
● Hold more data than CD- ROMS.
● Can store larger applications. ● Data transfer rate is slower
● Videos is higher resolutions. compared to other storage medium.
● Very large storage capacity 4.7-9 Gb ● Have to buy a separate DVD
● Sound and picture quality is excellent, player.
making them ideal for storing films ● DVDs do not work in CD drives
with video and sound. ● They can be easily damaged by
● DVD drives can read CDs breaking or scratching

Blu-Ray disks
Use:
● Blu-Ray disks uses a blue laser instead of red laser used with CD/DVD ROMs.
Blu-Ray disks are normally used to stored:
○ HD Movies
○ Large Software/Game Applications

Advantages: Disadvantages

● Large storage capacity used to store ● More expensive compared to other

HD video content. optical media.
● Access Speeds are greater than other ● Separate player required –more
optical medium. expensive.
● Secure Encryption System to ● Not all movie titles available on
minimise chance of copyright. Blu-Ray.
● Data access speed is faster than with
other optical media

AIS/2024-25/GR-7/ICT/Study material/ Storage media

 Solid-State Storage Devices
The term ‘solid-state’ essentially means ‘no moving parts’.
Solid-state storage devices are based on electronic circuits with no moving parts (no reels of
tape, no spinning discs, no laser beams, etc.)
Solid-state storage devices store data using a special type of memory called flash memory…
Flash memory is increasingly being used in a wide range of devices. Some examples
include:
● Small, lightweight USB memory sticks, available for many Gigabytes.
● Memory cards for digital cameras.
● Main internal storage for tablet computers (SSD)
● Digital audio players.
● Mobile phones.
● Video game hardware.
Solid State Drives:
● Supports reading/writing data & maintains stored data in a permanent
● Functions much like a hard drive but different technology
● Built with an array of semiconductors that form its memory and operated using an
integrated circuit
Use:
● Used to store operating systems and working data
● Used for storing application software
● Used in file servers for computer networks
Advantages: Disadvantages
● Faster than hard disks because they ● More expensive than hard disks
do not need to ‘spin up’ the disk ● Have a smaller capacity than
● Robust because no mechanical parts modern hard disks
● Read performance is fast even when
data fragmented
● Less susceptible to data loss
● Lighter, quieter and require less
power than hard disks

Flash Drives/Memory Sticks

Otherwise called pen drive/memory stick/USB stick
Can store several GBs of data and use solid state technology
Connected to a computer through USB port and power to operate drawn from host
computer
Use:
● Used to transport files between computers

Advantages: Disadvantages

● Very compact and ● Not possible to write protect the data and files
portable media ● Small physical size and are easy to lose.
● Very robust ● Lower storage capacity than hard disk

AIS/2024-25/GR-7/ICT/Study material/ Storage media

Memory Card:
A form of electrically erasable programmable read only memory (EEPROM)
Use:
● Used to store photos on digital cameras
● Mobile phones use them as memory cards
● Used in MP3 players to store music
● Used as a backup in hand held devices

Advantages: Disadvantages
● Not possible to write protect the data and
● Very compact and portable files
media ● Small physical size and are easy to lose.
● Very robust ● Lower storage capacity than hard disk

Backing Up Data
What is a Backup?
A backup simply means making one or more copies of your data.
For example, if you have a folder of photos stored on the hard-drive of your laptop, you
might back them up by copying them to a CD-R.

Why Backup Your Data?

If you delete a file by accident, your computer breaks, your laptop is stolen, or your
business burns to the ground, having a backup copy means that you have not lost your
precious data. You can recover your lost files and continue working.

How Are Backups Created?

Personal backups :
● Burning files to a CD-R
● Copying files to an external hard-drive
● Copying the files to another computer on a network

Businesses backup essential data by…

● Making copies of data very regularly
● Using large-capacity media such as magnetic tape
● Keeping old copies of backups, just in case
● Automating the system so that nobody forgets to do it!
● Keeping backup media off-site (in case of fire or theft)

Units of storage
Everything in a computer is stored as 1s and 0s. A single 1 or a single 0 in a computer is
called a 'bit'. If we store a character in a computer it takes eight 1s and 0s, so we might say it
takes eight bits to store a character.

1 bit = One Binary digit (0 or 1)

1 Byte=8 Bits
1024 Bytes =1 Kilobyte (KB)
1024 Kilobytes =1 Megabyte (MB)
1024 Megabytes = 1 Gigabyte (GB)
1024 Gigabytes = 1 Terabyte (TB)
1024 Terabytes = 1 Petabyte (PT)

AIS/2024-25/GR-7/ICT/Study material/ Storage media