Transcript Computer Systems Operating Systems

Computer
Systems
Operating Systems
An operating system controls all the tasks the
data
into the
computer• Loads
does for
you
memory from the Hard Disk
Sends text and
graphics to the
screen
Reads in data
from keyboard
and mouse
• Saves your files to disk
Sends data to
your printer
Examples of Operating Systems
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•
•
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Microsoft Windows
Apple Mac OS X
Linux
Android
But NOT things like: Microsoft Word,Games,
Internet Explorer
These are programs that run on your computer
Operating System
• When you are designing an Information
System you have to make sure that the
computer system that it is going to run on has
the correct operating System!
Standard Functions of the OS
• User interface (HCI)
– The OS provides the means of the user
communicating (interacting) with the computer
system
– Features such as windows, icons, menus,
commands, etc. are all provided by the operating
system
1011
0110
Open
word
processor
OS
Standard Functions of the OS
• Controls input/output
– The access to all devices attached to the
computer is controlled by the OS.
Standard Functions of the OS
• Manages memory
– Controls where programs and data are placed in
the main memory.
• Error Reporting
– The operating system lets the user know if any
mistakes have occurred
• E.g. No paper in printer
Checking!
•
What jobs does the Operating System do?
•
Give an example of an Operating System for
–
•
a) a PC b) a tablet c) a mobile phone
What does the user interface do?
Processor and Memory
The two most important parts of the inside of
the computer are the processor and the
memory.
The processor is the “brain” of the computer
where the computer works things out.
The memory is where the computer
“remembers” things for the processor.
The Computer’s Memory
Computers use main memory and backing storage to store
data.
Main memory is the fast memory inside a computer that stores
data the CPU is currently using
Backing store is the bigger but slower memory that stores files
and programs for the computer
Backing store comes in two types – magnetic and optical.
Magnetic – Hard Disk and Floppy disk
Optical – CDROM and DVD
USB Flash drive
Main memory
• Inside the computer there is main memory
• Main memory is made up of memory chips
• There are two kinds of main memory:
RAM – Random Access Memory
ROM – Read Only Memory
Random Access Memory
• RAM is where the computer stores data
that is it currently using. This includes:
– Data from the keyboard as you type
– Data from open files and programs you
are using
• When you turn off your computer, all the
data in RAM will be lost.
• This is why you must always save files to
backing store before turning off a
computer!
Memory Chips
Read Only Memory
• ROM is READ ONLY –
• A ROM memory chip is sealed: you can’t
change it
• The computer can read the data in the ROM
straight away when the computer is
switched on
– This is why parts of the OS are sometimes
stored on ROM
• It isn’t wiped when the computer is switched
off
How to measure memory
• We said before that everything in a computer is either a 1 or a 0
• This is because computers use binary numbers
• The size of memory is usually given in megabytes or gigabytes,
but what does that mean?
Bit
Byte
Kilobyte
Megabytes
Gigabyte
Terabyte
Binary digit: a 1 or 0
8 bits, e.g. 01101100
1024 bytes
1024 Kilobytes
1024 Megabytes
1024 Gigabytes
Memory size
Bit
Byte
Kilobyte
Megabytes
Gigabyte
Terabyte
Binary digit: a 1 or 0
8 bits, e.g. 01101100
1024 bytes
1024 Kilobytes
1024 Megabytes
1024 Gigabytes
So an iPod with 60GB of storage space has:
60 x 1024 x 1024 x 1024 x 8
= 515,396,075,520 bits!
(over 515 billion bits…)
The Processor’s speed
• Processors work at different speeds.
• The faster the speed the more operations it
can carry out in 1 second.
• The speed is measured in GHz
• 1 GHz represents 1 billion cycles per second
• Here are some processor speeds
• Intel Atom Z540 @ 1.86GHz
• Intel® Core™ Solo Processor T1400 1.83 GHz
The Processor
The processor is a very important part of a computer
system.
It is the brains of the computer
A processor takes data in, processes it and then outputs the
data to screen or printer.
Print out
calculation
mouse
Input
Process
Output
keyboard
Display on
screen
Checking…
• Explain why you can not store data in ROM
• What happens to RAM when the computer is
switched off? Why should this be ok?
• Explain why the speed of a processor is
important.
Processor Types
• There are different types of processors
– solo core processors with only 1 processor.
– Multiple core processors e.g.
• Duo core: with 2 processors
• Quad core: with 4 processors
• Octo core : with 8 processors
– Low power processors for mobile devices like
smartphones and tablets.
Storing graphics
A graphic can be a drawing, graph, painting or
photograph.
Graphics are made up of a grid of pixels.
A pixel is a single point on the screen.
Storing Graphics
• In black and white graphics, the grid of pixels
can be represented by binary numbers
• 1 stands for a black square, 0 stands for a clear
square.
• Each pixel takes up 1-bit to store.
The grid is 8 x 8 pixels, so it
will take 64 bits to store.
1
0
0
1
1
0
0
1
0
1
0
1
1
0
1
0
64 bits is 8 bytes.
0
0
1
1
1
1
0
0
0
0
0
1
1
0
0
0
1
0
0
1
1
0
0
0
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
0
0
0
0
0
0
0
1
0
How many bits do you
think it will take to
store this graphic?
Working out graphics file sizes
• Task: how much storage space does a 2” x 2” black
and white graphic need with a resolution of 300
x300?
• Number of pixels = 2 x 2 x 300 x 300
• =360000
• A black and white graphic needs 1 bit per pixel
• Storage space needed = 360000 bits
• Divide by 8 to turn into bytes
• = 360000/8 bytes = 45000 bytes
Working out graphics file sizes
• Divide by 1024 to turn into kilobytes
• = 45000 /1024 kilobytes = 43.94 kilobytes
Colour Graphics
• To store colour graphics, we need to assign
each colour a different number e.g. red = 1,
blue = 2 etc.
• These colour codes are stored in binary
• The larger the binary number, the more
colours we can have. How many do we need?
• 32-bit graphics are normal (4.3 billion
different colours)
Hardware
• Now its time to look at the hardware that
makes up a computer system.
Backing Storage
Backing storage memory is used to store
files when the computer is switched
off, and are usually removable.
There are three types of backing
storage, Optical, Magnetic and solid
state.
We’ll look at magnetic first.
Hard Drive
Hard Drive
Hard drives store data by writing
magnetic patterns onto metal disks.
The surfaces are divided up into sectors
and tracks which allows each part to be
accessed directly.
•The disk is in a sealed box to prevent dust damage.
•The read/write head is just above the surface of the disk
•The disk spins between 7,000 and 10,000 rpm
•They hold gigabytes / terabytes of data
Hard drives
Internal Hard drives are
inside the body of a
computer system
External Hard Drive
• External Hard drives are outside the body of a
computer system and are connected by an
interface like USB 3 or Thunderbolt. They are
usually compact
and portable.
Interfaces
• USB 2
• Universal Serial Bus 2 – speed – 480 Megabits
per second
• USB 3
• Universal Serial Bus 3 – 4.8 Gigabits per
second
• Thunderbolt - 10 Gigabits per second
Megabit, Gigabit
One megabit per second (Mbps)
=
one million bits per second.
one gigabit per second (Gbps)
=
one billion bps.
Optical Backing Storage
Optical backing storage uses laser optics to
read and write data.
Data is stored in binary by using lasers to burn
microscopic marks on the disk surface.
Data is read by reflecting light off the surface to
read the microscopic marks.
Using Laser optics
CD-ROM
• High Capacity - 700 Megabytes
• Stores data in microscopic grooves
• Read Only
DVD-ROM
• Works in the same way as CD-ROM
• Stores more data because it uses a narrower laser beam to read
and write to disk
• Ordinary DVDs hold 4.7 Gigabytes
• Double-sided, multilayered DVDs store up to 17GB
• Enough space for large files such as movies
CD-R
• Stands for Compact Disk Recordable
• Uses a layer of dye which laser changes to store data
• CD-Rs are WORM - Write Once Read Many
– Once files are written on, they can’t be deleted or changed
– CD-Rs are read-only after they are written
CD-RW
• Stands for Compact Disk Re-writable
• Unlike CD-R, these can be rewritten
• This is because they use the laser to change the reflective
properties of microscopic marks
• CD-ROMS, CD-Rs and CD-RWs are used for:
– backing up large files
– Storing large multimedia presentations
– Storing large programs, like games
• CD-ROMS, CD-Rs and CD-RWs are slower than hard disks
• But they are removable!
DVD-R and DVD-RW
• Works in the same way as CD-R and CD-RW
• Stores more data because of narrower laser
• Can store up to 4.7GB
Solid State
• Solid State drives store data on rewritable
memory chips
• They are commonly used in
small portable drives commonly
called ‘ memory sticks’
Solid State
Solid State drives are also found inside Pcs,
tablets and portable external drives.
Solid State Advantages
• Speed: Solid State drives are very fast.
Unlike Hard drives they are not slowed down
by moving mechanical parts.
• They offer data transfer rates up to 600
Mbytes per second ( Hard drives offer to up to
140 MB/s )
• Reliability: they do not break down as
easily as a hard disk because they have no
moving parts.
Solid State
• Disadvantage
• Cost: the cost per Gigabyte is much
higher than a hard drive.
Input Devices
Input devices are pieces of hardware
that let you control a computer by
sending data into the computer.
Mouse
A mouse lets you
control the pointer on
screen, and click to
select icons.
Mice usually have 2
buttons and sometimes
a scroll wheel.
Trackball
A trackball is similar to
a mouse except the ball
is on top. The trackball
does not move around
the desk like a mouse.
They are useful when a
user does not have
desk space to move a
mouse, and for people
who find it hard to use
their arms to move
objects around.
Trackpad
A trackpad is a small
pad that senses the
movement of your
finger.
It lets you control the
mouse by moving your
finger across the pad.
You can click by
tapping the trackpad.
Graphics Tablet
A flat plastic panel with electronic sensors below the
surface detect the movements of a pointing device.
Very accurate – used by graphic artists / designers /
Computer Aided Design (CAD)
Touch Sensitive Screens
Touch Screens
• These are very popular input devices and are
found on our desktop computers, tablets &
mobile phones
Keyboard
Input text and numbers
Function keys
QWERTY layout
Very common, nearly every computer has one
Scanner
Used to input drawing,
photographs from
paper.
With Optical Character
Recognition (OCR)
software it can
recognise writing on a
page.
Digital Cameras
Digital Cameras
• Captures light coming through the
lens and stores a digital image
• Allows instant review of picture taken
• Delete photos you don’t like
• Stores images in a memory card {
solid state}
Choosing a camera
Look at the accuracy (resolution) –
measured in Megapixels. Does it have a
zoom lens?
What capacity is the memory card?
Digital Video cameras
• Captures light coming through the lens and
stores a series of digital images
• Needs a large storage capacity – video
takes up a lot of space (15 frames per
second)
• Usually have a small LCD screen to view
your video
• Features: zoom, focus, lighting, infrared
recording, on-board editing
Webcams
Usually built into monitors Can
be connected to a computer
via USB or built into screens
Useful for video calls via MSN
Messenger or Skype
Output Devices
• Output Devices are used to get data out of
your computer.
• The output devices you need to know about
are: printers, plotters, monitors and speakers.
Laser Printer
Uses a laser beam to copy image of a
page onto light-sensitive drum
Ink (toner) attracted to the drum then
transferred to paper
 Laser printers are fast
 The output is high quality
 Colour laser printers are expensive to
buy but relatively cheap to maintain.
Sprays ink onto the paper
Printout quality is high
Cheap to buy, can be expensive
to maintain (expensive ink)
Slower than Laser Printer
Inkjet Printer
Comparing printers
You compare printers according to
• Speed. Printer vary in the time they take to print
a page. The speed will usually be shown as
pages per minute (ppm)
• Resolution. The quality of the printout varies
according to the number of dots per inch (dpi)
used.
• Costs:
Initial cost: the cost of buying the printer.
Running costs: cost of toner or ink
Plotter
Uses inkjet technology to
produce large, accurate and
complex drawings
Used by architects / designers
Quicker than drawing by hand
Monitor
Screen used to display
computer output
Different monitors have
different resolutions
The higher the resolution, the
more detailed the picture will
be.
Screen resolution
• Resolution is the number of pixels displayed
on the screen
• It is usually given as width x height
• Examples of High resolution :
1280x1024
1920x1080
LCD / TFT Displays
LCD = Liquid Crystal Display
These screens have the following advantages:
Flat, light, needing little power, can be run
from a laptop battery
The one disadvantage is that sometimes they
are not bright enough and can cause eye
strain
LCD / TFT Displays
TFT = Thin Film Transistor
Same advantages as LCD.
Uses a tiny transistor to form each pixel
Can update the image very quickly, allowing it
to handle complex graphics and animation
which LCD displays cannot
Task 13c
• Why are high resolution monitors needed?
High resolution monitors are needed for CAD
work and art work.
• Why are LCD screens suitable for laptop
computers? They are flat, light and need little
power so can run from batteries.
• What type of LCD screen would you want if you
were showing lots of animations?
TFT (Thin Film Transistor)
Desktop VS Laptop
Desktop computers stay
in the same place.
They are bigger and heavier than laptops but
this does not mean they are more powerful than
a laptop. That depends on the processor and
the memory they have.
Laptop
• Laptop computers are small and compact
• They weigh a lot less than a desktop – usually
1.5 – 2kg
• Runs off battery, charges from mains
• Has a flat screen (LCD or TFT)
• Has a keyboard , trackpad
speakers and built-in webcam
Supercomputer
• Large and powerful
• Lots of processing power (multiple processors) and
many terabytes of RAM
• Used for e.g. weather forecasting, research in the oil
industry, scientific research
• Edinburgh University has a very powerful
supercomputer
Tablet computers
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•
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Tablet computers are very popular
They are light portable computers
Weight between 0.3 and 1 Kg
Screens
– LCD or TFT
– Screen size between 7 and 12 inches
– Screen resolution around 1200 x 800
– They have touch screens with an on-screen
keyboard
Tablet Computers
Smartphones
• Smartphone are powerful mobile computing
devices
• They have
– A mobile operating system
– Media player
– Camera: { still and video}
– GPS navigation
– Touchscreens
– Access to the Internet
Smartphones
• Smartphones can download a wide range of
software application : ‘Apps’