Transcript Standard Grade Computing Studies Commercial Data Processing

Higher Grade Computing Studies
4. Peripherals
Input Devices
• Keyboard
• Mouse
• Scanners
• Microphone
• Digital Camera
• Digital Video Camera
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices - Scanners
• A scanner can be used to digitise (turn analogue data into a
digital image) images/photographs.
• The resultant digital representation of the scanned image is a
bitmap.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices - Scanners
• Hardware features of scanners:
• Resolution - the number of pixels/dots per inch (dpi). The
greater the dpi the better the quality of the image produced.
• Bit depth - the number of bits used to represent the
colours of a pixel. The more colours available then the fine
differences between the colours can be shown.
• Interface – how its connected to the PC, i.e. USB.
• Accuracy – the resolution and bit depth capacity of the scanner
will determine how close the computer image is to the original.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices - Scanners
• Advantages
• cheaper than a digital camera.
• can scan existing photographs.
• can be used for other purposes.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices – Microphone/Sound
• Sound is an analogue waveform.
• So it needs to be converted to digital signal for it to be
stored in a computer.
voltage
represents a 1 bit
represents a 0 bit
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices – Microphone/Sound
• The sound signal is captured and recreated by sampling. The sampling
rate determines how many samples
are taken of the analogue signal every
second. The sample measurement is
stored using a number of bits, called
the sampling resolution.
Sample
taken from
signal.
• Accuracy - the higher the sampling rate and the higher the
sampling resolution, the more accurately the sound signal is recreated.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices – Microphone/Sound
• Music recorded digitally onto a CD is sampled 44,100 times
per second (sampling rate) using 16 bits (sampling resolution).
• Capacity : a 2 minute sample from a CD will require
44100 * 16 * 120 = 80.75 Mb.
• To reduce file sizes, we can use compression.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices – Digital Camera
• A digital camera obtains an image which is converted into
digital data and stored in a flash card.
• Accuracy - this will depend on the array of photosensitive
sensors. The more sensors and the smaller they are, the higher
the resolution giving better detail and sharper edges.
• Capacity - this is based on the resolution and the number of
images that can be stored. The higher the resolution the fewer
images that can be stored.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices – Digital Camera
• A digital camera captures images which are 1600 * 1280
pixels in size and use 65536 colours. Calculate the storage
requirements for an image from this camera.
Number of pixels = 1600 x 1280 = 2048000
65536 colours are represented using 16 bits or 2 bytes
Storage = 2048000 x 2 bytes = 3.9 Mb
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Input Devices – Digital Video Camera
• A video capture board is needed to generate digital video.
• A video using a screen size of 640 * 480 pixels and 24 bitdepth will require 23Mb per second. So the video capture
board must be able to compress the video as it is being
captured.
• Accuracy - this will depend on the quality of the source as
well as the resolution settings on the board.
• Capacity - most memory cards can hold 1Gb or more.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Storage Devices
• Floppy disk
• CD-ROM, CD-R, CD-RW
• Hard drive
• DVD-R, DVD-RW, DVD+R,
DVD+RW and DVD-RAM
• Magnetic tape
• You should be able to describe all of the above in terms of their
capacity, speed and cost.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Storage Devices – Solid State Devices
• USB Flash Memory - A USB flash memory is a memory chip
with a USB plug. It uses EPROM technology.
• Memory Card Reader/Writer - The card is placed in the USB
memory card reader/writer, which is then recognized by the
system as an external drive. The files can be transferred to and
from the card.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Storage Devices – Solid State Devices
• There are two types: flash ROM and flash RAM. Flash RAM
needs power to retain its data and flash ROM does not.
• Flash ROM is used in flash cards (for storing digital camera
photographs) and memory sticks (or MP3 players).
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Production of a Multimedia Catalogue
• You would need a high specification computer with the
following …
• A fast processor to run applications quickly and view video and hear sound/music at
an appropriate speed.
• A large amount of RAM to open media elements - video, sound etc, and run
software.
• A large hard disk to store media elements - video, sound etc, while creating the
catalogue.
• A DVD writer to store finished catalogue for transport to customers/clients.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Production of a Multimedia Catalogue
• A firewire/USB 2.0 interface to attach a camera to download pictures and video.
• A video card to capture pictures and video.
• A sound card to record sound/music.
• A high resolution monitor to view media elements.
• A digital video camera to record video frames.
• A microphone to record sound.
• A scanner to capture images from photographs, etc.
• A high resolution colour laser printer to print out the catalogue.
• Speakers to play back audio.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Setting up a LAN
• You would need a high specification computer with the
following …
• A fast processor to run applications at an appropriate speed.
• A large amount of RAM to open media elements - video, sound etc, and run
software.
• A large hard disk to store client software.
• A Network Interface Card to connect to the network.
• A monitor to view data or software.
• Cables to allow the computer to connect to the network.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Setting up a LAN
• Hubs to connect devices to the network.
• Switches to filter and forward packets on the network.
• A network laser printer to print documents across the network.
• A network server to store user files across the network.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Developing a School Website
• You would need a high specification computer with the
following …
• A fast processor to run applications at an appropriate speed.
• A large amount of RAM to open media elements - video, sound etc, and run
software.
• A large hard disk to store software.
• A Network Interface Card to connect to the network.
• A video card to capture pictures and video.
• A sound card to record sound/music.
• A high resolution monitor to view data/media elements.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Developing a School Website
• Cables to allow the computer to connect to the network.
• Digital Video Camera to take digital photographs and video.
• Scanner to capture images from photographs, etc.
• Inkjet printer to print out completed pages for checking.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Buffers
•A buffer is an area of computer memory that is allocated to
transferring data between the computer and a peripheral.
• A buffer will be used when a fast acting part of the system is
exchanging data with a slow acting device e.g. a printer.
• Most interfaces have buffers to store blocks of data while in
transfer between the processor and the peripheral. This ensures
that the processor is not held up by slow communications to
and from the peripherals.
• The buffer must also keep the status of the peripheral so that
the processor knows when it is able to send or receive data.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Spooling
• Another approach to ensuring the processor is not held up by
slow peripherals is to send data to be spooled. This means that
the data is sent to fast backing storage usually a hard disc.
• The data is then sent from the backing store to the peripheral
in the gaps between processing actions (an example of this is
background printing).
• The
user can continue operating the computer while the data is
being sent to the peripheral.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing
• Peripheral devices, such as printers, scanners, magnetic tape
drives and hard disk drives, connect to processor.
• Each device works at different speeds, use different codes,
transfer different amounts of data at a time and even work at
different voltages.
• In
order for these devices to communicate with the CPU they
need to be interfaced.
• An interface is a unit that sits between the CPU and a peripheral
device to ensure compatibility.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing – Data Conversion
• Data to be communicated has to be converted in such a way to
be understood by the hardware or software doing the sending or
receiving.
• Some
data is sent by parallel data transmission, some by serial
data transmission.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing – Data Conversion
Receive
Transmit
• Parallel data transmission Each bit of an 8-bit byte is
sent at the same time along
a set of parallel wires. The
intention being that all bits
of the byte arrive at their
destination at the same time.
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1
0
1
1
0
0
1
0
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing – Data Conversion
• Parallel data transmission
• Advantages
• Faster than sending out a single bit at a time
• Good for transmission over short distances
• Disadvantages
• Skewing can occur, due to interference, where the
individual bits may arrive at their destination at
different times.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing – Data Conversion
• Serial data transmission - each bit of an 8-bit byte is sent one
at a time, over the communications line.
Receive
Transmit
0
Start
Bit
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1 1 1
0 0
7
Data Bits
1
0 0
1 1
Parity
Bit
Stop
Bits
Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing – Data Conversion
• Serial data transmission
• Advantages
• Only one data channel required
• Good for transmission over long distances
• Disadvantages
• Slower than parallel transmission.
• Start and stop bits required to identify different pieces
of data.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing
• Data Conversion - Data to be communicated has to be
converted from the format understood by the processor to the
format understood by the peripheral and vice versa, e.g. serial to
parallel, analogue to digital.
• Voltage Conversion - As devices operate and send signals at
differing voltages then these quantities must be converted to
allow successful communication, e.g. one device may use 5v for
a 1, while another device may use 7v for a 1.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Interfacing
• Data Storage - Data is stored in buffers inside the interface as
it is transferred from the processor to the peripheral and vice
versa.
• Protocol Signals - The conversion of different protocols to
and/or from the processor and the peripherals.
• Status Signals - Supplies status signals to the processor
indicating the readiness of the peripheral device to transmit or
receive data.
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Higher Computing
Computer Systems
S. McCrossan
Higher Grade Computing Studies
4. Peripherals
Wireless Communication
• Some peripherals now have the ability to communicate with
the CPU without physical connection (i.e. cabling).
• Bluetooth is an example of wireless technology. It is a short
range radio technology aimed at simplifying communications
among Internet devices and between devices and the Internet. It
also aims to simplify data synchronisation between Internet
devices and other computers.
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Computer Systems
S. McCrossan