3.2 Input & Output Devices
Input Devices
Output Devices
– barcode scanner
– actuator
– digital camera
– digital light processing (DLP) projector
– keyboard
– inkjet printer
– microphone
– laser printer
– optical mouse
– light emitting diode (LED) screen
– QR code scanner
– liquid crystal display (LCD) projector
– touch screen (resistive, capacitive and infrared)
– liquid crystal display (LCD) screen
– two-dimensional (2D) and threedimensional
– speaker
– 3D printer
-(3D) scanners
Compiled by Reema Rifkhan
Compiled by Reema Rifkhan
3.3 Storage Devices
Primary Storage description:
What Primary storage is
What Primary storage stores
Compiled by Reema Rifkhan
What is RAM?
RAM is a computer’s primary memory. It is a very fast solid state storage medium that is
directly accessible by the CPU.
Any open programs or files on a computer are temporarily stored in RAM whilst being used.
Benefits of RAM
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•
Directly accessible to the CPU, making processing data faster
Fast solid state storage, making processing data faster
Drawbacks of RAM
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Relatively expensive memory
Volatile – any data stored in RAM is lost when power is removed
Purpose of Secondary Storage
Data can be permanently stored
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… meaning that (application) software can be loaded/retrieved
… meaning that operating system can be loaded/retrieved
… meaning that user data/files can be accessed/retrieved
Examples of data stored in secondary storage devices:
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Applications
Operating System
Device Driver software
General video, audio, image files
Why is HDD not used as primary memory ?
would cause a computer to perform much slower (a HDD or SSD is not directly accessible to the CPU,
and isn’t as fast as RAM).
Compiled by Reema Rifkhan
Primary VS Secondary Storage Devices
Primary
Directly accessed by CPU
Both Volatile and Non Volatile storage
media
Stores less data
Data access time is less
Secondary
Not directly accessed by CPU
Non- Volatile storage media
Stores more data
Data access time is more
Types of Storage devices based on technology.
Type of storage
How the technology works
Examples
Magnetic
Hard Disk:
• Data is stored on the surface in
sectors and tracks in magnetic platters
• Platters spin
• Read-write heads consist of
electromagnets that are used to read
data from or write data to the
platters.
• Laser is shone at the disk
• An (arm/head) moves the laser across
the surface of the disk
• The laser burns pits onto the surface
of the disk
• The laser is used to read the pits and
lands on the surface of the disk
• The reflected light from the laser
shining on the disk is captured (by a
sensor)
Hard Disk, Zip Disk, Jazz Disk,
Floppy DIsk
Optical
SSD
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Uses flash memory
Data is flashed into silicon chips
Uses NAND and NOR technology
Uses transistors to control the flow of
electrons
When data is stored, transistor values
change from 0 to 1 or vice versa
Writes and reads data sequentially
CD (CD-RW, CD-R)
DVD
Blu-RAY
SSD Drive
Flash Pen Drives
Flash Memory Cards
Compiled by Reema Rifkhan
HDD vs SSD technology for internal storage
Benefits of flash memory
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Portable, small and lightweight
Durability, flash has no moving parts to damage
Range of capacities available
Fast speeds, with no moving parts of boot up time
Drawbacks of flash memory
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Limited (but huge) number of write cycles possible
Really high capacities are uncommon
In relative terms, an expensive storage option compared to a HDD
Optical Storage Devices
Type
CD
DVD R, DVD RW,
DVD ROM
DVD RAM
Track
single continuous
spiral
single continuous
spiral
Many Concentric
tracks (The advantage of
Storage capacity
700 MB
Laser type
Red
4.7 GB
Red
4.7 GB, or 9.4 GB
Red
25 GB – 128 GB
Blue
using concentric tracks is that
data can be read from and
written to the disk at the
same time.)
Blu-Ray
single continuous
spiral
Compiled by Reema Rifkhan
How does Blu-Ray hold more data than DVD?
Use of blue laser means smaller wavelength so pits and lands in the disc are much smaller so
more data can be stored.
How does DVD Hold more data than CD?
DVDs also use a smaller laser than CDs, however they also employ the method of using multiple
layers
Virtual Memory
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If the amount of available RAM is exceeded due to multiple programs running, it is
likely to cause a system crash.
This can be solved by utilizing the hard disk drive (or SSD) if we need more memory.
virtual memory is RAM + swap space on the hard disk or SSD.
How Virtual Memory Works
In computer operating systems, paging is used by memory management to store and
retrieve data from HDD/SSD and copy it into RAM.
A page is a fixed-length consecutive (or contiguous) block of data utilised in virtual memory
systems.
Advantages of virtual memory
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programs can be larger than physical memory and still be executed
there is no need to waste memory with data that isn’t being used (e.g. during error
handling)
It reduces the need to buy and install more expensive RAM memory
Disadvantages of virtual memory
•
Disk thrashing
Problem in a hard disk drive (HDD) caused by excessive swapping in and out of data causing
a high rate of head movements during virtual memory operations.
•
Premature failure of hard disk due to large number of head movements
Cloud Storage
Compiled by Reema Rifkhan
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Cloud storage is a method of data storage where data is stored on remote servers.
The same data is stored on more than one server in case of maintenance or repair, allowing
clients to access data at any time.
3.4 Network Hardware
Basic hardware needed to create a network:
1. Router: a device that enables data packets to be moved between different networks and assigns
IP addresses to devices on a network.
2. NIC (Network Interface Card): a hardware component (circuit board or chip) that is required to
allow the computer to connect to a network, such as the internet
3. Transmission Media: the cables (or wireless media) that is required to transfer data in a network.
NIC
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There are two types of NIC: Wired and wireless.
Most modern NICs are wireless.
Wired NICs require a cable to be attached to the NIC to connect to the network such as an a
ethernet cable while a wireless NIC allows wireless connection.
NICs are assigned a MAC address.
MAC address
A unique identifier which is used to identify a device on a network; it takes the form NN-NN-NNDDDD-DD, where NN is the manufacturer code and DD is the device code.
Features of a MAC address
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set to identify a device
it is a unique (address)
represented as a hexadecimal number (6 pairs of hexadecimal numbers=48 bits)
it is a static address // it does not change
it is set by the manufacturer
the first part is the manufacturer ID / number / identifies the manufacturer
the second part is the serial number / ID
Example of a MAC address
Compiled by Reema Rifkhan
82:4A:8F:23:EE:4F
(try it out: Convert the number to binary to form the 48 bit equivalent binary address)
Routers
Router reads data packets it receives and forwards to the destination computer using IP address of
the destination computer.
Router will use the MAC address to forward the data packet if the destination computer is within the
local network. To forward over the internet, it uses the IP address.
IP Address
It is identified either as IPv4 or IPv6; it gives a unique address to each device connected to a network
identifying their location
Features of IP address
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Set to identify a device on a network
Can be IPv4 or IPv6// 32 bit or 128 bit
Can be static or dynamic
May not necessarily be unique
Assigned by ISP
Static Vs Dynamic IP Address
Static: Static IP addresses are permanently assigned to a device by the internet service provider
(ISP).
Ex: Remote server, Online Database, FTP server
Dynamic: Dynamic IP addresses are assigned by the ISP each time a device logs onto the internet.
This is done using Dynamic Host Configuration Protocol (DHCP).
Compiled by Reema Rifkhan
IPv4 vs IPv6 Address
IPv4
32 bits
Uses denary
4 groups of 8 bits
Groups separated by a dot “.”
IPv6
128 bits
Uses hexadecimal
8 groups of 16 bits
Groups separated by a colon “:”
Why was IPv6 introduced?
the use of only 32 bits by IPv4 considerably reduces the potential number of devices and routers
used on the internet at any one time, so a newer version called IPv6 is now used which uses 128 bits.
Advantages of IPv6 over IPv4
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removes the risk of IP address collisions
has built-in authentication checks
allows for more efficient packet routes
Similarities between IP Address and MAC address
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Both addresses can be used to identify a computer/device
Both are unique
Both can be represented as hexadecimal
Both addresses do not change if IP address is static
Differences between IP Address and MAC address
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An IP address is assigned by the network/router/ISP, A MAC address is assigned by the
manufacturer
An IP address can be changed (if dynamic), MAC address cannot be changed
IP address has 4/8 groups of values, MAC address has 6 groups/pairs of values
IP address is 32-bit/128-bit, MAC address is 48-bit
IP address does not contain serial number/manufacturer number, MAC address does
IP(v4) address is denary and MAC address is hexadecimal
Compiled by Reema Rifkhan