Computer Systems Operating Systems An operating system controls

Computer Systems

Operating Systems An operating system controls all the tasks the • Loads data into the computer 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 • • 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?

Memory size So an i. Pod with 60 GB of storage space has: 60 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 Z 540 @ 1. 86 GHz • Intel® Core™ Solo Processor T 1400 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 Output Input mouse Process 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. 64 bits is 8 bytes. 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 x 300? • Number of pixels = 2 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 17 GB • 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. 7 GB

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 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 : 1280 x 1024 1920 x 1080

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 13 c • 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 – 2 kg • 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 • • 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’