N4 Computer Systems

N4 Computer Systems

1. Computer System Diagram

2. CPU Central Processing Unit

   •    A rough way to tell how fast a processor can work is by measuring it’s §Clock speed This is measured in Hz, (hertz). The faster the clock speed, the faster a processor can work.   1 Gigahertz (GHz) = 1000 million pulses per second  1 Megahertz (MHz) = 1 million pulses per second
   • Input Devices
     •    These are pieces of computer equipment which allow users to enter data into a computer.   
     • Hardware - Peripheral
       •    A peripheral device is a single item of hardware attached outside the processor.    Hardware are the physical parts of the computer system. In simpler terms, parts of the computer you can touch.  
     • Keyboard
     • Mouse
     • Trackpad
     • Joystick
     • Graphics Tablet
       • Used mostly with C.A.D. (Computer Aided Design). It is a pressure sensitive pad which the user presses to control the actions on the screen.   
     • Scanner
     • Microphone
     • Digital Still Camera
     • Digital Video Camera
     • Webcam
     • Magic Wand Keyboard
       •    This is used when a user does not have the ability to use a standard keyboard or mouse.   They place the wand in their mouth and press down on the keyboard to select the key they wish.  
     • Touch Talker
       •    Again used when the user cannot use a  standard keyboard or mouse.   The user presses the pictures on the pad and the computer makes a sound to represent the picture.  
     • VR Data Gloves
       •    This is a computer generated version of the real world. The input devices required to interact with the computer generated world are:-   Data Gloves   These are gloves fitted with sensors so thecomputer can take information from the user’s hand movements
   • Output Devices
     • Devices
     • Monitor
       • VV.D.U Visual Display Unit
         •    V.D.U. -  Visual Display Unit made up from a monitor and a keyboard.   
       • Thin Film Transistors
         •    Thin Film Transistors. AKA Plasma. This type of screen has a different transistor to control every pixel. This makes the quality of picture much better.   
       • LCD Liquid Crystal Display
         •    This is the type of monitor which is found on laptops. LCD’s were developed as they were light weight and portable.   They are not as good quality as TFT’s.  
     • Printers
       •    Printing speed is measured in pages per minute (PPM) The output produced by a printer is called a HARDCOPY.   
       • Inkjet
         • use ink   are cheaper to buy than laser printers are more expensive to run than laser printers   
       • Laser
         •    use toner are expensive to buy compared to inkjet printers cheaper to run than inkjet printers can print at a faster speed than inkjet printers   
     • Speakers
     • Headphones
     • Multimedia Projector
       •    This is a device which takes output from the computer and projects the image onto a surface.   Often used with smartboards.   Used for giving presentations to large groups of people.  
   • Main Memory
     •    This is used to stored data and programs being used by the  processor.   
     • RAM Random Access Memory
       •  Used to temporarily store programs and data that are currently in use   Contents are lost when computer is switched off   
     • ROM Read Only Memory
       •  Used to permanently store programs and data   The contents of these chips remain after the computer is switched off.  You cannot save information onto R.O.M. chips.  Data/Programs stored there by the manufacturer when the computer is being built.   Stores the Bootstrap loader (part of the Operating System)  
     • Memory Units
       •  A BIT is a Binary Digit, either a 1 or a 0.   It is the smallest unit dealt with by the computer system.     1 byte = 8 bits 1 kilobyte  = 1024 bytes   1 megabyte = 1024 kilobytes   1 gigabytes = 1024 megabytes  1 terabyte  = 1024 gigabytes
   • Backing Storage
     •    These are where data and programs are stored by the computer permanently.   
     • Magnetic
       • Floppy Disks
       • Hard Disk
         •    Magnetic form of backing storage.   This is located inside the computer, or external  series of magnetic disks one on top of another. Advantages   Very large storage capacity.   Very fast speed of access, (random/direct access to data).   Disadvantages  Expensive.
         • Hard Disk Drive (HDD)
         • Solid State Drive (SDD)
       • Magnetic Tape
         •    Magnetic Tape - mainly used for backups     Advantages   • Very large storage capacity.   • Cheap.   • Portable     Disadvantages • Slow to retrieve data (sequential access to data).  
       • Universal Serial Bus (USB)
         •    These use chips to store information, similar to RAM and ROM chips.   They use solid state technology.   Advantages   Cheap.   Portable.   Fast to retrieve data (random/direct access to data). Large storage capacity, (continually getting bigger). Robust – it has no moving parts and therefore is less easily damaged.Disadvantage Are small and can be lost easily.
     • Optical
       • CD's
         • Compact Disks     700Mb capacity – low in comparison with the alternatives. Optical storageOptions CD ROM – Read only CD Rewriteable – data can be added and removed with new data added. 
         • CD=RW
         • CD-ROM
       • DVD's
         • Digital Versatile Disks   4.7 Gb capacity – far greater than CDs.   Optical storage  Options  DVD ROM – Read only  DVD Rewriteable – data can be added and removed with new data added.  
         • DVD-RW
         • DVD-ROM
     • Back Up
       •    A backup is an extra saved copy of your work on any backing storage device.   It should be made regularly.   It should be kept away from your original saved copy.   
   • Single Core
     • This means that there is only one processor dealing with all the computer functions/processes   
   • Multi Core
     •    This means that there is more than one processor dealing with all the computer functions/processes   This can enhance computer performance   
   • Registers
     •    §Registers - Temporary storage locations for data/calculations while its being processed   
   • Arithmetic and Logic Unit
     •    §Arithmetic & Logic Unit - Does all the calculations and logic statements (IF’s).   
   • Control Unit
     • Tells the processor what to do and when to do it.

3. System Requirements

   •    To be used efficiently, all computer software needs certain hardware or other software resources to be present on a computer.    These are known as system requirements   With increasing demand for higher processing power and resources in newer versions of software, system requirements tend to increase over time.   
   • Hardware Requirements
     •    Hard-disk requirements vary, depending on the size of the software to be downloaded/run    Quality display adapters are required to run better than average computer graphics and games.   The speed of the processor is essential for any software to run well.   Some software applications need higher performance peripherals  e.g. network devices.   
     • Hard-disk Capacity
     • Display Adapters
     • Processor Speed
     • Higher performance peripherals (devices)
     • Connectivity
       •    If connection to the internet there are various other pieces of hardware which may be required:-   Modem   Router   Hub   Switch   Network Interface Card (if you are using a wireless connection you would need a wireless NIC) Transmission media (which you will learn about later in this unit)   As well as this hardware you will also need :-   An account with an Internet Service Provider (ISP)   Browser/Communications software   
   • Software Requirements
     • Operating System
       •    A computer’s Operating System is a series of programs which run the computer.   Different computer systems have different operating systems.   e.g.  Microsoft Windows 8
       • Data Input
       • Data Output
       • Main Memory Management
       • Data Storage (Backing Storage)
       • Error Reporting
       • HCI Human Computer Interface
     • Memory Requirements
     • Software Drivers
       •    Software Drivers make use of special hardware devices such as display adapters to make the computer perform its best.   

4. Networking

   • Emerging Technologies
   • Security Risks
     • Virus
       •    A computer virus is a piece of program code that, like a biological virus, makes copies of itself by attaching itself to another program. The virus can waste the host's resources and sometimes destroyor change files. While viruses are usually malicious - destroying data or crashing network services - many do nothing or are just annoying  (for example, displaying a message to the user). Many viruses are made to wait a long time before doing anything, usually destroying data on a certain day, like a holiday.   Viruses are usually spread by a computer network, by e-mail, or by removable media, like a memory stick.   
     • Worms
       •    A computer worm is a computer program that makes lots of copies of itself, like a computer virus. The main difference between the two is that a computer virus attaches itself to another computer program, but a worm works by itself. As well as copying itself, a worm can be made to do all sorts of things,  like delete files on a computer, or send e-mails to everyone the  owner has in their address book   
     • Trojans
       •    A type of 'malware' software. A Trojan seems to do an useful task and so the user will use it. But in the background, the Trojan is also carrying out its real purpose which is hidden and unknown to the user. For example, you download a free game, it's great! You keep on using it. But meanwhile the Trojan may also install a permanent keylogger that now tracks every keystroke you make and sends it off over the Internet to whomever created the Trojan.   
     • Prevention Method
       • Anti-Virus Software
         •    This is referring to software that can detect the presence of a virus within a computer file and warn you there is a problem. The anti-virus software may then offer to 'quarantine' the file so it cannot be used to spread the virus. Many packages will also try to remove the virus, but this is not always successful.   
       • Firewall
     • Hacking
       •    This is gaining unauthorised access to someone else's device/computer or files. There are many reasons hackers do this:- Ø  To steal data Ø  To steal money   To steal someone’s identity
   • LAN Local Area Network
     •    This is when the computers which are communicating with each other are in the same building or site. - school, office, or university ADVANTAGES:    §Information can be shared/passed between all users on the network §Network users can communicate with each other using email §Peripherals can be shared - printers, scanners §Data can be stored centrally, so users can use any computer to access their data §Access to the network can be limited by using unique user ID’s and passwords §Access to data and programs can be limited by using levels of access   
     • Transmission Media Type: Wired CABLES
       •    UTP - unshielded Twisted Pair or Optical Fibre   
       • UTP Unshielded Twisted Pair
       • Optical Fibre
     • Transmission Media Type: Wireless
       • Infrared Communication
       • Bluetooth
       • WiFi (Wireless Fidelity)
   • WAN Wide Area Network
     •    §This is when the  computers which are communicating with each other are further apart - a town, a country, the world §The most commonly used W.A.N. is the internet. This is open to anyone in the world with a computer, modem and ISP (Internet Service Provider). §A W.A.N. can be owned by a single company and can be limited to employees of that company/organization.   
   • The Cloud
     •    §This is when Internet Service Providers (ISPs) provide computer services which means businesses/cloud customers do not need to buy large computer systems and networks.      §This means the cloud customer does not own the servers and backing storage devices that their data is stored on. §Customers rent out storage space on their ISP’s server.     Advantages to customers:-  •   Customers have access to powerful computing infrastructure, (mainframe servers). •   Can have access to a vast range of software at a much reduced cost. •   Have access to technical support.   Disadvantages:-   •  Security of sensitive company data is in the hands of the ISP, not the company.  
     • ISP Provides service
       • Software
       • Backing Storage
       • Servers
     • Basic computing devices need to be purchased by the Business
       • Desktops
       • Laptops
       • Tablets