Computing Notes.docx

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University of Guelph
Computing and Information Science
CIS 1200
Scott Schau

Computing Notes QR Codes: marketing technique, brings you to specific web site Crowd sourcing:  consumers review products  smart companies use this information to improve products Podcasts  audio/video file, requires media player  RSS (real simple syndication) technology  automatically updated Webcasts  not auto updated  streaming media technology Voice over Internet (VoIP)  allows calling over the internet Listservs  blog type posts recieved through being part of an emailing list E-Commerce  Business-to-consumer: ex. amazon  Business-to-Business: businesses sell things to one another  Comsumer-to-consumer: ie. ebay Internet Security  look for security company logos on sites when doing online transactions  only do online transactions of well known reputable sites  look for padlock (IE) or key (netscape) icon  https:// as opposed to just http:// means it is secure Spam: mass emailing from unwanted sources cookies: text files saved to computer that speed up web pages, enable a page to remember and load users preferences adware: software downloaded with other software downloads Spyware: often hidden with other downloads, monitors browsing, sends info back to server Security Threats  Hackers: anyone who breaks into computer unlawfully, they can be dangerous when they get personal and bank information  Trojan Horses o program that appears to be useful, but does something malicious o can often allow a hacker to take full control of your computer, oh no! o Safeguards:  firewalls: programs /hardware designed to keep computer safe from hackers  securing wireless network:  change network name (SSID)  disable SSID broadcast  change password on router  turn on security protocols  implement media access control  Viruses + Worms: o programs that attach to a host program and spread to other computers when files are exchanged o spread through downloads and running files o malicious side effects! ie. produce annoying messages, reformat hard drive, loss of data, destroying files o categories:  boot sector: loads upon booting, often transmitted by USB left in port while booting  Bombs:  Logic Bombs: triggered when certain task is done; ie. opening a file  Time Bombs: triggered on certain date/ time  Worms: self-replicating programs, use vulnerabilities in operating system to travel btwn networks  Scripts: hidden on websites  macro virus: attached to documents such as word files  email viruses: use your address book to distribute viruses to contacts  encryption virus: search for data files, compress them using encryption key, user then has to pay to get unlocked o Classifications (by method they avoid detection):  polymorphic: periodically rewrite themselves to avoid detection  multipartite: infect multiple file types  stealth: erase their codes and hide in active memory o Defences:  antivirus software:  looks for specific virus signature (code unique to specific virus)  deletes or quarantines virus (puts virus in a safe place)  **** antivirus must be up to date in order to fully protect someone as new viruses are made all the time! URL parts:  protocol (rules) used to retrieve info (usually http)  ://www  domain name  subdirectories (specific pages within domain) Internet Basics:  a client/server based network  Dial up connection: connect using telephone line  broadband connections: cable, satellite, DSL  Cable: uses coaxial cable & cable modem  DSL: uses phone line& DSL modem  Fibre optic: o transmits data by sending light through optical fibers o faster and more costly  satelite: uses dish and coaxial cable  wireless Software  computer programs, allow hardware to perform specific tasks  application software: programs to carry out specific tasks  system software: operating system, enables hardware to work together Operating Systems  manage hardware (processor, memory, storage, peripherals)  provides means for software applications to work with CPU  scheduling, management and interaction of CPU tasks, RAM storage, and virtual storage  system maintenance & file compression  now: people use 64 bit operating systems, as opposed to 32 bit, this is faster but not compatible with 32-bit programs  types: o real-time O.S.: perform one repetitive task (ie. ATM, digital picture frame) o single user, single task OS: perform 1 task @ a time, for single user (PDAs) o Single User, Multitask OS: regular computers o MultiUser OS: network operating system with lots of users on single system  platform: combination of OS & processor  user interface: o enables interaction with computer  old computers were command driven: had to type in codes to command  then computers were menu driven: users scrolled through menus to do tasks  now: graphical user interface: command with graphics and mouse (point and click)  processor management: o OS arranges times for executing processes o when multitasking, OS ranks tasks by priority o Hardware interruptions:  devices (like a printer) become highest priority  CPU pauses what it is doing to attend to interruption  OS puts task that is on hold in RAM stack, then goes back to it after  memory storage management o OS uses RAM as temp storage of stack of instructions to be performed, accesses this info when ready o OS responsible for space allocations in RAM, and clearing items after use o responsible for coordinating swap files in temp memory when not enough RAM  file & device management o devices come with device drivers that allow device to communicate with OS o ***Plug and Play (PnP) included on windows allows users to use some hardware and software to immediately without installing a device driver  booting up: o basic input/output system activated (BIOS)by powering CPU o BIOS checks that attached files are in place o OS loaded into RAM o configuration & customization settings are checked  file management is organised in a hierarchical fashion by OS  naming files: name given to file, followed by .filetype Utility Programs  small apps that perform special functions like disk fragmentation, system restore and add/remove software Business Software  customer relationship management software: store, organise customer contact info  enterprise resource planning systems: o billing, production, inventory, HR o vertical market software: tailored to specific indistry o proprietory software: tailored to specific company  computer aided design: 3d modelling, used by engineers and architects Web-Based Software  program hosted by website, no installation required Freeware  copyrighted software you can use for free Beta Versions  often free  still under development  developers hope users report errors/ bugs for further improvement Shareware  software users can test  run for a limited time free of charge Open Source  free under the condition that any changes made to the software must be distributed for free System Software  Productivity Software o word processing, spreadsheets etc o database software: electronic filing systems o personal info management software: calendars, notepads, to-do lists etc o productivity software: wizards (step by step guides), templates etc  Media Software Hardware Systems Units: hardware in the computer itself Peripheral Units: things attached (monitor, keyboard, mouse, printer)  Input Devices o keyboards, scanners, webcams etc  Output Devices o monitor, printer, speakers etc Terms  motherboard: circuit board, holds CPU, RAM, expansion cards  RAM vs. ROM o RAM: temporary memory o ROM: start up instructions, permanent memory  CPU: central processing unit (brain of computer!)  Hard drive: main storage  Drive Bays: hold computer components  Ports: connect external hardware (ie. USB)  LED vs LCD monitors o LCD more energy efficient, better colour, thinner Binary Language:  combinations of 8 0s or 1s, these combinations represent a letter, number or symbol  each 0 or 1 = a binary digit  combination of 8 = 1 byte  ASCII code: coding system that represents letters, numbers and symbols. Uses 1 byte (set of 8 binary digits) for each symbol  Unicode: ASCII did not have enough combinations for some other language's symbols, unicode uses groupings of bytes (groups of 8 set of binary digits) to accommodate How the computer uses binary code:  Switch Board uses 1's to turn on electrical signal and 0's to turn off, creating usable information for computer  Transistors in comp. made out of semiconducting material (can both conduct & insulate electricity) makes up switch board.  Microprocessor holds billions of transistors in the form of an extremely small chip RAM:  temporary /volatile storage  fits in slot in motherboard  has significant impact on performance of computer  what it does: o temporarily stores instructions/ data for processor o processor accesses these when ready to process them o operating system responsible for coordinating space allocations for RAM o operating system clears items from RAM when no longer needed  due to new technology, RAM storage space increases by about 60% every year Hard disk Drive  non-volatile storage  largest storage capacity of any storage device  fastest transfer of data to other computer components (referred to as transfer rate)  made of several coated platters, data saved as magnetized spots on these, "arms" read/write on platters  **** when not enough RAM for temporary storage of instructions, hard disk space called a swap file is borrowed, referred to as virtual storage. Swapping (also known as paging) makes your computer sluggish! Portable Storage includes flash memory, flash drives, usb, cds and dvds Video Cards  attach to motherboard  a type of expansion card that translates binary data into images  includes ports to connect to diff. video equipment  controls # of colours monitor can display o 4-bit = 16 colours o 24-bit= 16 million colours Audio  system consists of speakers and sound card  types o amplified speakers: better quality, external power o unamplified speakers, internal power Sound Cards  attach to motherboard  enable sound  *most computers use 3D sound card CPU: Central Processing Unit (Brain)  found on microprocessor, which is found on the motherboard  processing power of CPU determined by number of transistors on microprocessor (processing power of new computers doubles every 18 months due to advances in technology)  composed of 2 units: o control unit: manages switches inside CPU o arithmetic unit: does all the calculations...  CPU cycle: o fetches required data from RAM o decodes info/instructions into understandable language for computer o executes instructions o stores in RAM, repeats process  System clock; controlled by a vibrating crystal, allows CPU to work at a constant speed called clock speed (measured in MHz & GHz)  Cache Memory: blocks of memory on and next to microprocessor, create a holding place for most used/ recent instructions/data for quick retrieval o level 1 cache: on CPU chip, for commands just used o level 2: next to CPU chip, on microprocessor o level 3: next to microprocessor o Buses  electric wires in computer circuitry  "highway" for data  types: o local buses: on motherboard, run btwn CPU & main system memory o expansion buses: run btwn audio or video cards and motherboard  the wider the bus, the faster, measured in bus clock speed (MHz) Faster Computers:  Methods: o pipelining: allows CPU to work on more than 1 task at a time o dual processors: 2 parallel CPU chips on 1 motherboard Computer Networking Computer Network: 2 or more computers connected via software and hardware in order to communicate  facilitate info sharing  allow users to share peripherals  transfer files to and from computers without external storage Node: device connected to network, ie. computer, printer etc Router: enables you to share broadband Internet connections Peer to Peer Networks (P2P):  each node can communicate directly with every node on network  common home network  Types: o wired ethernet networks:  use Ethernet protocol for nodes to communicate  requires installation of network adaptors to each node  most comps have these network adaptors preinstalled  transmission media: UTP cable, which is also used in phone lines  switches: act as traffic signal, helps data packets avoid running into each other and being damaged  routers: transfer packets of data btwn 2/more networks, if network is connected to internet, router needed to send data btwn the networks o wireless Ethernet networks:  uses radio waves instead of wires as transmission media  needs network adapter: either expansion card (NIC) or USB device  *wireless network adapters contain transceivers, translates electronic data into radio waves, broadcasts waves to network nodes, receive signals from other networks o Client/Server Networks:  usually have 10/more nodes  contains 2 diff types of computers: o Client computer: users accomplish specific tasks, make specific requests o Server Computer: provides info or resources to client on network  Internet is client/server based Local Area Network (LAN):  networks in which nodes are located within small geographical area ie. home or school computer lab Wide Area Network (WAN):  made up of LANS connected over long distances  ie. can connect LANS from 2 different campuses in order to communicate between campuses Home Area Network(HAN):  made up of LANS connected within a home Network Components:  Networks all include: o means of connecting the nodes (cables or wireless) o devices that allow nodes to communicate/ send data to eachother o software that allows network to run  Transmission Media: o connect nodes to each other o types:  can use existing wiring (phone lines/ power lines)  can use additional cable  wireless networks, which use radio waves o Data Transfer Rate (bandwidth): max speed data can be transmitted between 2 nodes  Network Adaptors: o devices connected/installed to network nodes o enable nodes to communicate with each other and access to network o can be USB ports or expansion cards (NICs: network interface cards) inside computer  Network Navigation Devices: o data sent over transmission media in bundles called packets o net. nav. devices help make data flow possible o simple networks: devices built into network adaptors o more sophisticated networks use:  routers: transfer packets of data btwn 2/ more networks.  switches: receive data packets, send them to node on same network Networking Needs  Dedicated Servers: used to fulfill 1 specific need (ie, handling emails)  Authentication Sever: keeps track of who is logging on to network, which services available to each user  File Servers: store/ manage files for network users  Print Server: for a network with centralised printing service  Application Servers: store/distribute application software for each system on network  Database Servers: dedicated to organizational to database storage, queries , retrievals  E-mail Server: handle incoming, outgoing,= and internal email  Communications server: handles communications within network / btwn other networks Network Topology  refers to the physical/ logical arrangement of computers, transmission media and network components  Types: o Bus Topology:  uses single cable/ "bus" to handle transmission btwn networks  often used in P2P networks  all nodes can communicate  data collisions may occur, to avoid this, nodes "listen" to data traffic, go when no other node is transmitting data o Ring Topology:  nodes laid out on a circle  data flows around circle in one direction like a traffic circle o Star Topology:  most widely deployed client/server network layout in businesses  offer most flexibility  nodes connect to central communications device, called switch  "Active Topology" b/c switch transfers data signals Data Collisions:  CSMA/CD (Carrier Sense Multiple Access with Collision Detection) used on Ethernet networks to avoid collisions  allows node to determine that no other nodes are transmitting data signals  If 2 devices begin transmitting data at same time, and have not detected one another, data collision occurs  when this happens, jam signal sent to all nodes alerting of collision  nodes stop transmitting, wait random amount of time before transmitting their data signals Types of Transmission Media  Wired media typically used in large networks for transmission, best type of cable determined by: o Max run length: over which signals can be "heard" by nodes o Bandwidth: amount of data that can be transmitted in certain time o Bend Radius (flexibility): amount of bending allowed before damage occurs o Cable cost o Installation Costs o Susceptibility to Interference o Signal Transmission Methods  Coaxial Cable & Twisted Pair Cable: send electrical pulses to transmit data
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