Ict Notes

Hardware and Software Hardware: physical components that make up a computer system (keyboard, mouse) Software: programs that control the computer system with 2 types Systems software: allow the hardware to run properly Applications software: allow the user to do specific tasks Components of Computer Systems A computer is made up of hardware and software with: Input devices (inputting the data into the computer)- keyboard, mouse Output devices (data output from a computer)- monitor, printer Secondary storage devices- DVD R/W drive, removable hard drive important part of the computer system consists of: CPU- interprets the commands from the computer hardware and software -contains coding like BIOS to tell what the computer should carry out RAM- internal chip where data is temporarily stored when running applications ROM- storing informations that needs to be permanent Hard disk- computer’s main memory Operating Systems * Controls the operation of the input, output and backing storage devices * Supervises the loading, running and storage of application programs * Deals with errors Maintains a computer log with the details of computer usage Examples: CLI (Command line interfaces): A user will type in instructions to choose options from menus, open softwares and more. (Commands need to be memorised to carry out basic operations)

*Combination of letters and words, basically codes* GUI (Graphical user interfaces): A user will interact with a computer using pictures or symbols rather typing in a number of commands. (WIMP is used for PCs where a cursor moves and select icons)> Daily life screen Types of Computers PCs and Laptops: PCs have separate monitor, mouse and keyboard and laptops, have all in 1 -PCs are not portable and laptops are -Laptops have short battery life Mainframe computers: -Large computer system for jobs which require large memories and very fast processor time -Used for banking and insurance Backing up data * Copying of files and data to a different medium like disk, drive and more in case of a problem in the main storage device. It is important to do so because: -Data could be lost due to failure of the original storage device -Hackers could corrupt the data In case a file needs to be used somewhere else Types of access * The way data is stored and read by different backing storage devices. Serial access: -Used on magnetic tape systems where the speed of access is not important like in utility billing. -When the magnetic tape needs updating, a new magnetic tape is used to merge the old data and the new data. Direct access: -Using magnetic disks and optical media. -Computer uses a key field to calculate where data has been stored then it is able to access the data directly from the calculated position. -Fast so used in online systems

Backing storage media * All computer systems have some form of backing storage and have 3 types of magnetic, optical and solid state. Examples here are using magnetic data: Fixed hard disk -Main method used for data storage -Usually stores disk operating system (DOS) -Fast data transfer rate and large memory capacity -Easily damaged and not portable Portable hard disk drives -Same way as a fixed hard disk but connected to the computer by a USB -Used as back up systems to prevent losing data -Data transfer rate is fast and large memory capacity -Can be damaged if dropped Optical storage media CDs and DVDs all use optical read or write methods unlike tapes and hard disks. * They are all used to store music or film at least. Examples: CD-ROM and DVD-ROM -Can’t be written over and can only be read -Data is stored as a series of pits and lands in the metallic optical layer -Hold more data than floppy disks but data transfer rate is slower than hard disks CD-R and DVD-R -Recordable once only -Used for store data to be kept for later use

-Cheaper than RW disks -Not all CD/DVD players can read these CD-RW and DVD-RW -Can be written over several times -Used in CCTV systems Able to use different file formats each time -Expensive DVD-RAM -Writing and reading can occur at the same time -Written many times -Used in satellite receivers -Have a long life (30 years) -Large capacity -Expensive -Not as compatible as R or RW format Solid state backing store Memory sticks -Able to store several Gbytes of data -Used for transporting files -Very portable and robust -Easy to lose because of their small size Flash memory cards -Form of EEPROM -Used in mobile phones, digital cameras, MP3 to store data like music, photos -Compact, can be removed and used in other devices Expensive per Gbyte of memory compared to a hard disk Computer Networks * When computer systems are connected together to form a network. * Ranges from a few computers (homes, schools) to large networks like the internet. Common types of network Most networks are controlled by the use of servers like: * File servers- allow user to save and load files * Applications servers- deal with the distribution of application software to each computer * Printer servers- ensure printing from devices on the network is done * Proxy servers- used as a buffer between WANs and LANs.

Different types of networks LAN (Local area network) -Within one building -Consist of a number of computers and devices -Connected to hubs or switches. -Hubs or switches are then connected to a router and modem to allow the LAN to connect to the internet which becomes part of a WAN. -Shares resources and communicates between users -Easier spread of viruses and slower access to external networks *WAN, wide area network is formed by a number of LANs connected together through a router or a modem*

There are 4 different types of LAN network topologies: Ring -Every computer is connected in a ring and data in transmitted in that cycle -Work well under heavy loading -If there is a fault in the wiring between 2 computers then the whole network will fail -Unpopular topology Bus -Each computer is connected to a common central line and data travels along this line -Easy to add a new computer to the network -If 1 computer fails, doesn’t affect the rest -If the central line has a fault, then the whole network fails. Star Each computer is connected via a central hub or switch and data is sent to the hub which then sends out data along every cable -If 1 computer fails, doesn’t affect the rest -Easy to expand the network -If central hub breaks down, the whole network crashes Tree -A central line connects together a series of star networks. -If 1 computer fails, doesn’t affect the rest. -If central hub breaks down, the whole network crashes. WLAN (Wireless local area network) -Similar to LAN but no wires or cables and provide wireless networks over short distance -APs are connected into the wired network at fixed locations -Adding new computers is very easy Data transfer rate is slower than a LAN WiFi -Any system is possible to connect to a network like laptop computer, peripheral devices -Accessible in WiFi hotspot whether free or paid in public places Bluetooth -WPAN -Possible to create a small home network -Allows communication between a PDA, mobile phone, computer and more -Range is small (10m) Network Devices * Modems- converts a computer’s digital signal into an analogue signal and also does the reverse * Network Hubs- hardware devices that can have a no. f devices/computers connected to take data received via one of the ports and send it out to all of the ports

* Switches- similar to hubs but distributes data more efficiently * Bridges- connect 1 LAN to another LAN that uses the same protocol and examines the message in between these LANs * Routers- connect the LANs together and also connect them to the internet * HTTP proxy servers- buffer between a WAN and a LAN and passes on the service requests to the internet and passes back the requested pages Internet * A worldwide collection of networks allowing a user to send, receive emails, chat or browse the WWW (a web browser which allows the user to display pages and files from the web) * The web is made up of millions of websites and web pages. Web pages -Contains documents on a computer screen with multimedia. Website: – Many of web pages linked together -Shows hyperlinks to allow users to navigate (blue underlined text) Web browsers: -Use URLs to retrieve files -URLs are a way of locating a resource on the internet -Either a set of four numbers 121. 234. 456. 78 or an alphanumeric form docs. google. com/school/ 3 ways of accessing the internet: dial-up, cable, internet via DSL Intranet A computer network based on internet technology that is designed to meet the internal needs for sharing informations within a single company. -Safer, less chance of external hacking or viruses (behind a firewall giving protection) -Prevent users from accessing unwanted websites (possible to block out certain internet sites) -Requires password entry Network Security User ID- needed when logging on to any network system Password- combinations of letters and numbers (personal) Encryption- converting data into a code or encoding it Authentication techniques- proving who you are e. g. banking (PIN, bank card, fingerprints) Communication methods Fax- documents are scanned electronically and converted into a bitmap image.

Email- sending text and attachments from 1 computer to another Video conferencing- communication between people at 2 separate locations (save travel costs, dangerous to fly but time differences) VOIP- talking to people using the internet (bad sound quality with echoes, spamming, phishing, but free) Health and Safety * Backaches- adjustable chairs and correct posture * RSI to fingers and wrists- use ergonomic keyboards and take regular breaks in between * Eyestrain and headaches- use anti-glare screens Modelling Applications * A simulations is the creation of a model of a real system in order to study the behaviour of the system. * Used in traffic control systems, design of buildings/bridges These computer models have the advantage of: -Saving money -Find a solution more quickly and safer

Simulations are used because they are: -Less expensive to build than the real thing (like building a bridge) -Some tasks are impossible to try out in real life -Faster to do a simulation than the real thing Batch processing applications * This is most commonly used in billing, payroll and cheque processing. * A number of tasks are all collected together then processed all at once. Payroll (to calculate wages and print out pay slips for employees) -Inputs: employee details from file like rate of pay, bank details and number of hours worked. -Processing done: calculation of gross pay, any deductions -Outputs: printed payslips, transferring to BACS

Billing systems (bills are sent out on a pre-determined date) -Inputs: customer details, bank account details -Processing done: calculation of number of units of that particular thing used (e. g. electricity) -Outputs: bill showing all the details Robotics These are used in areas of manufacturing from heavy work to delicate operations like: -Welding bodywork on cars -Paint spraying of car bodies Programming of the robot to do a certain task is done by 2 ways: -Robot is programmed with a sequence of instructions which allow it to carry out the task -A human operator manually carries out a task and how each task is done is then relayed back to the robot (embedded processor) Robots’ advantages/disadvantages: Work in environments that are harmful to humans -Work non stop -Replace skilled labour leading to unemployment -Risk of de-skilling Online booking systems * Have the ability to update files immediately and prevents double booking * Used for transport systems, cinema tickets When booking a ticket for a movie: -Customer types in details of the type of movie, time, date they want. -The database searches for the availability of the movie and shows the seating plan. -Then seat numbers and total price is shown. -After confirmation, the seats are no longer available for other people. -Customer enters details of him/herself and selects a specific payment. An e ticket is then sent to their email as a proof of purchase Banking application Computer technology is used for banking transactions like internet banking, chip and PIN technology. ATMs machines where customers can get cash using their credit/debit cards and are very convenient. But: -Often in places where theft can be done -An outsider might be able to see the PIN code you key in. Chips and Pins

* Many credit cards are equipped with a chip and a magnetic stripe containing informations like the PIN. (used to improve security) * When a chip or a PIN card is used to pay, a form of EFT takes place. Library systems * LIbrary systems are computer controlled. A barcode or a magnetic stripe is used on the books being borrowed an on the borrower’s library card. Consists of 2 files: -Book file: contains barcode, book title, author and more. -Borrower’s file: contains borrower’s number, name, details of books borrowed How it is used: -When a borrower takes out a book, the book’s barcode is scanned and the details are found on the book file. -The borrower’s library card barcode is then scanned for the borrower’s number. *Here, the book file is linked to the borrower’s file and both files are updated to indicate which book has been borrowed and its due date* Control systems * Consist of a computer or a microprocessor. Handles data from sensors and send signals to output devices and interface box to convert signals between sensors and the processor * Computers are widely used because they can run for 24 hours, 365 days and process data quickly * Used to control traffic light, security (burglar alarms), air conditioning/ heating in large buildings Components used: -Microprocessor: CPU of a computer made up of thousands of chips to remember information and process programs -Sensor: measuring physical quantities like temperature, pressure and send signals to the processor -Interface box: some data like temperature and pressure are analogue data and this converts these data into digital where the computers can read them