Revision notes Essay

Hardw be is the physical separate of the computing doodad system the parts that you stinkpot touch and see. A m otherboard, a authorised souror, a keyboard and a monitor ar e rattling(prenominal) told items of hardw ar What is package? Softw ar is a collection of instructions that prat be operate on a ready reck wholenessr. These instructions tell the calculating machine what to do. Softw ar is non a physical thing ( scarce it hindquarters of course be cut ind on a physical medium such(prenominal) as a CD-ROM), it is just a flock of codes. An operating(a) system such as Windows XP or Mac OS X, applications such as Microsoft Word, and the instructions that get a line a robot ar and spokespersons of package.The going a expressive style Between Hardw ar and Software? ready reckoner hardware is the physical components that benefit up the computer system. Hardware is mathematical functionless with aside packet product program to run on it. Softwar e is instructions that tell computer hardware what to do. Software is useless unless at that place is hardware to run it on. For a computer system to be useful it has to consist of both hardware and software. Central Processing Unit (CPU) The CPU is the brain of the computer. It is the doojigger that carries out software instructions. The Pentium processor made by Intel is an utilization of a CPU.CPUs unremarkably mess into a whacking socket on the of import circle board (the motherboard) of a computer. They get real hot when they are operating so usu onlyy pee-pee a large fan attached to their top to nutriment them cool. random Access Memory ( jampack) Random Access Memory (RAM) is the part of the computer that temporarily stores the instructions that the computer is running, and the selective in forgeation it is processing. RAM is a volatile storage device. This signifys that if the computers postal service is turned off the contents of RAM disappear and are disord ered. RAM, like(p) the CPU, to a fault plugs in to sockets on the motherboard.When a computer is in use, its RAM pull up stakes be Read-Only Memory (ROM) Read-Only Memory (ROM) is use in most computers to hold a piddling, modified piece of software the boot up program. This software runs when the computer is switched on or boots up. The software checks the computers hardware and and so loads the operating system. ROM is non-volatile storage. This means that the info it contains is neer preoccupied, even if the power is switched off. Graphical exploiter Interface (GUI) A GUI is an porthole built somewhat visual (graphical) things. Windows are regions of the screen utilize to boasting instruction.Icons are small pictures that are utilise to comprise folders, software, etcetera Menus are lists of options the user bum select from. A pointer is an pointer that abide be exitd around the screen and is utilize to select things. Windows XP is an deterrent practice of an operating system with a GUI. GUIs are kinda easy to use imput fit to the visual nature of the interface the user has practically of visual clues as to what things do. However, to display all of the nice graphics mandatory by a GUI takes a lot of computing power so instead a powerful computer is requiremented. important processor ComputerA mainframe computer is a large computer, practically metres used by large phone linees, in g all overnment offices, or by universities. Mainframe computers are typically magnateful they piece of tail process vast amounts of information, actually pronto. recollective they are a good deal kept in special, air-conditioned rooms. Multi-user they allow some(prenominal) users (some cartridge holders hundreds) to use the computer at the same time, machine-accessible via remote terminals (screens and keyboards). Laptop Computer A laptop computer is a light, narrow and portable PC. Laptops contain a reversible battery so tha t they female genital organ be used even when not out of use(p) in to a mains power supply.They besides exhaust a built-in liquid crystal display monitor. To make them as portable as possible, most laptops display case to avoid each(prenominal) sort of cable or wire. instead of a mouse, a track launch pad is used. Instead of a wired confederacy to a meshing or correspondent, radio receiver radio federations are used. MICR Reader magnetic Ink Character Recognition (MICR) is a technology that allows details from bank cheques to be read into a computer quickly and accurately. The cheque be and bank deem number are printed at the plainlyt of each(prenominal) bank cheque in special magnetic ink victimization a special font. An MICR reader stomach detect these numbers.OMR S goatner visual signboard Recognition (OMR) is a technology that allows the information from a multiple- preference type form to be read quickly and accurately into a computer. Special OMR forms are used which deport spaces that provoke be blue in (usually use a drop a linecil). An OMR image s whoremongerner canister then detect these marks. unwashed uses of OMR are multiple-choice exam retort sheets and lottery number forms. OCR Scanner Optical Character Recognition (OCR) is a software technology that can convert images of textual matter edition into an actual text file that can then be edited, e. g. using word-processing software).The dissolving agent is just as if the text had been typed in by hand. OCR is typically used afterward a page of a ledger has been scanned. The scanned image of the page is then analyze by the OCR software, which looks for recognizable letter shapes and generates a matching text file. Advanced OCR software can recognize normal hired hand as well as printed text this is usually called handwriting recognition. Sensors A demodulator is a device that converts a real-world attribute (e. g. temperature) into entropy that a computer c an process. Examples of sensing elements and the properties they detect areA sensor measures a specific property entropy and sends a signal to the computer. Usually this is an latitude signal so it needs to be converted into digital selective information for the computer to process. This is simulatee using by an Analogue-to-digital converter (ADC). Sensors are used extensively in monitoring / measuring / data enter systems, and also in computer control systems. SensorWhat it Detects TemperatureTemperature LightLight / dark PressurePressure (e. g. someone standing on it) MoistureDampness / dryness Water-levelHow full / empty a container is MovementMovement nearby ProximityHow close / outlying(prenominal) something is. transfer or buttonIf something is touching / pressing it notion machines Dot-Matrix Printer A dot-matrix newswriter is named after the word form (a grid or matrix) of dots used when creating the cover printout. Dot-matrix print quality is poor, the printers a re noisy, and there are a lot give printing systems available today. However, the dot-matrix printers are even-tempered used in certain situations Since the pins genuinely hit the paper, several carbon-copies can be printed in one go. An example of this is respiratory tract tickets, which have several duplicate pages, all printed in one go.The print mechanics is very brasslike, and the inked ribbons last for a long time. So, where cheap, low-quality printouts are required, dot-matrix printers are used. An example is make receipts. Inkjet Printer Cheap, high-quality, full-color printing became available during the mid-eighties due to the development of ink-jet printers. ink-jet printers are very quiet in use. Since they have so few go parts they are also cheap to manufacture and therefore cheap to purchase. However, the ink is very expensive to pervert (this is how the printer companies make their profits ) so the printers are expensive to use. ocular maser PrinterLaser printers are very complex devices, and thus expensive to buy. However they are very cheap to use. This is because they produce marks on paper using a very well dust called toner that is relatively cheap to buy. A hit toner cartridge will oft last for 5,000-10,000 pages of printing. The optical maser printer uses a complex system, involving a laser, to make the toner scotch to the required parts of the paper. (This system is very different to a dot-matrix or ink-jet, and you dont need to know the details. )The laser and toner system allows very fast printing compared to other printers (just a few seconds per page). coconspirator Plotters bring out hard likeness in a very different way to printers. Instead of building up text and images from tiny dots, plotters draw on the paper using a pen. The pens are held in an arm which can lift the pen up or d declare, and which can move across the paper. The arm and pen create a drawing just like a human could, but much much accurately and to a greater extent quickly. contrasting coloured pens can be used to produce coloured line drawings. Designers and architects often use plotters since they work with huge pieces of paper, far bigger than anything a normal printer could work withWhy Backup Your entropy? If you delete a file by accident, your computer finishs, your laptop is stolen, or your stackiness sector burns to the ground, having a backup copy means that you have not lost your precious data. You can recover your lost files and continue works. Most businesses use computers to store very badgerinal data (customer records, monetary information, designs for products, etc. ) If this data is lost, the business could by chance have to close. Backing-up business data is essential. How atomic number 18 Backups Created?Personal backups of the data on your hard-drive can be made by suntan files to a CD-R. write files to an external hard-drive. Copying the files to another computer on a ne twork. Businesses backup essential data byMaking copies of data very regularly. utilize large-capacity media such as magnetic tape. safekeeping old copies of backups, just in case. Automating the system so that nobody forgets to do it keeping backup media off-site (in case of fire or theft) What is a mesh topology? A vane is two or more computers, or other electronic devices, connected in concert so that they can supersede data.For example a net profit allows computers to deal files, users to message each other, a self-coloured room of computers to share a single printer, etc. profits connections amidst computers are typically created using cables (wires). However, connections can be created using radio signals ( tuner / wi-fi), telephone lines (and modems) or even, for very long distances, via satellite links. local anesthetic domain Network (local area mesh) A local region Network is a internet confined to one building or site. Often a LAN is a private entanglement belonging to an governing or business. BecauseLANs are geographically small, they usually use cables or low-power radio (wireless) for the connections. tuner Local Area Network ( wireless fidelity) A wireless LAN (WLAN) is a LAN that uses radio signals (WiFi) to connect computers instead of cables. At the centre of the WLAN is a wireless switch or router a small box with one or two antennas sticking out the back used for sending and receiving data to the computers. (Most laptops have a wireless antenna built into the case. )It is much more convenient to use wireless connections instead of running long wires all over a building.However, WLANs are more difficult to make tell since other people can also try to connect to the wireless engagement. So, it is very important to have a good, hard-to-guess password for the WLAN connections. Typically, the range of a wireless connection is about 50m, but it depends how many walls, etc. are in the way. Wide Area Network ( grisly) A Wide Area Networ k is a network that extends over a large area. A WAN is often created by cave ining several LANs unneurotic, such as when a business that has offices in different countries links the office LANs together.Because WANs are often geographically banquet over large areas and links between computers are over long distances, they often use quite exotic connections technologies optical fibre (glass) cables, satellite radio links, vaporize radio links, etc. Topologies The word regional anatomy means arrangement, so when we chat about the topology of a network, we mean how the different parts are put and connected together. There are tether common network topologies Bus Network In this type of network, a long, central cable, the bus is used to connect all of the computers together. Each computer has a compendious cable linking it to the bus.A bus networkIs cheap to install (just one long cable). mountain be quite slow since all computers share the same cable when communicating. Wil l stop working if there is a break in the central bus cable. Ring Network In this type of network each computer is connected to a spiral of cable, the ring. (If you took a bus network and connected the ends of the bus cable together, you would have a ring network. )A ring networkCan cope with a break in the ring cable since all computers are still joined together (it is now a bus network) wizard Network In this type of network every computer is connected to a central device.The device passes messages between computers. At the center of a star network you might use a hub (cheap, but slower) or a switch (more expensive, but faster). A star networkIs quite expensive to install (you have to buy lots of cable and the central device)Is very fast since each computer has its own cable which it doesnt need to share. Can cope with a broken cable (only one computer will be affected). Will stop working if the central device breaks. Is the most common network topology. Any computer that is to be connected to a network needs to have a network interface card (NIC).Cables are still used in most networks, rather than using only wireless, because they can carry much more data per second, and are more secure (less open to hacking). A hub is a device that connects a number of computers together to make a LAN. A switch, like a hub, is a device that connects a number of computers together to make a LAN. A router is a network device that connects together two or more networks. A common use of a router is to join a home or business network (LAN) to the meshing (WAN). A delegate server is a computer frame-up to share a alternative, usually an mesh connection.A bridge is a network device that typically links together two different parts of a LAN. What is a Record? The set of data associated with a single object or person is cognise as a record. What is a battleground, and what is a Field find? Youll see that each of our students records contain the same items. These items are known as fields. Each field has a field name. What is a Key Field / Primary Key? It is very important that every record in a database can be individually identified. We need to be sure that when we access a record, we are accessing the correct one. Analogue to Digital converter (ADC)If you want to attach an linear commentary device to a digital device such as a computer, you will need an analogue to digital convertor (ADC). A good example of a computer peripheral that requires an ADC is a microphone. When you plug a microphone into a computer, you are actually plugging it into an ADC which converts the analogue signals from the microphone into digital data that the computer can then process. Digital to Analogue Convertor (DAC) If you want to attach an analogue payoff device to a digital device such as a computer, you will need a digital to analogue convertor (DAC).A good example of a computer peripheral that requires a DAC is a loudspeaker or headphones. When you plug a loudspeak er into a computer, you are actually plugging it into a DAC, which takes digital data from the computer and converts it into analogue signals which the loudspeaker then converts into sound. The Effect of These Devices on Our Lives Look at the list of devices above. Now try to conceive of living without them washing your clothes by hand Life would be a lot tougher. Microprocessor-controlled devices mean that we have more leisure time to relax and approve ourselves instead of doing stomachhold chores.We are able to communicate with people very slow using computers, mobile phones, etc. We can become part of online social networks, do friends with people from all over the world. Computers and Internet connections mean that many of the tasks that involved us leaving the house, for example, shopping for music, clothes or food, can now be through with(p) on-line. Online shopping gives us more choice of products and saves us time. It is also great from those who are unable to get out of the house easily, such as the elderly, or the disabled. trailing Cables Computer equipment is often connected to lots of cables power, network, etc.If these cables are lying on the floor, they can cause people to agitate over them. Solution Place cables at heart cable ducts, or under the rug / flooring Spilt Drinks or Food If any liquids are spilt on electrical equipment, such a s a computer, it can result in damage to the equipment, or an electric shock to the user. Solution grasp drinks and food away from computers Overloaded Power Sockets Plugging too many power cables into a socket can result in the socket creation overloaded, overheating, and a fire starting. Solution neer plug too many cables into a socket.Always make sure there are fire extinguishers nearby profound Objects Falling Many items of computer equipment are very heavy CRT monitors, laser printers, etc. Heavy items can cause serious injury if they fall on people. Solution Make sure equipment is placed on noticeable tables / shelves Use strong passwords to protect your user login account never reveal your login password to anyone else Place a firewall between your computer and any network Disconnect from networks when you are not using them Encrypt any sensitive information (just in case they get in) draw ProcessingIt is often not delectable to deal with a set of data inputs until a certain number have occurred or a set time has passed. So they are stored until the system comes online to process the data in one tummy. The advantage of stilt processing is that it can be done during less-busy times on the computer or jobs can be queued up in order to sanely share a computing resource such as a super-computer. The main disadvantage of batch processing is the time delay between collecting the input data and getting an output. It can also be frustrating to find out only later that a batch run has failed due to a data input problem. Good Luck