T171_PCAcknowledgements2007-03-27 16:35 - T171_PCThe content contained within this document is sourced from an Open University OpenLearnproject labspace unit T171_PC - .Licensing2007-03-27 16:35 - T171_PCThis work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0Licence.1: Software and hardware2007-03-27 16:35 - T171_PCWhen you think of a computer you probably think of the dull-looking box sitting on top of, orunderneath, your desk, plus the monitor, keyboard and mouse. These, along with all of thecomponents inside the computer box, are the physical parts of the computer - the hardware.But the hardware is just an expensive doorstop without something to make it work. For you toproduce your annual budget, write your great novel or draw your birthday party invitationsyou need programs which will make the computer do things. The computer also requiresprograms just to look after itself and to manage all its components. Programs are thesoftware. Therefore, in this module, when l refer to 'technology' l mean both hardware andsoftware, since the computer requires both to be a functional machine. You might like to thinkof the hardware as a car, and the software as the driver and the fuel it requires before it canbe driven. Hardware includes components such as the microprocessor, hard disk drive,memory chip, graphics card and so forth. Separate hardware items that are added onto thebasic computer unit, such as the monitor, modem, printer, keyboard, etc., are often calledperipheraIs. Software can be written in a variety of programming languages. A programminglanguage is used to express the instructions which tell the computer what to do in responseto a certain action. For instance, word processing software tells the computer to display theletter 'a' on the monitor when you press the 'a' key on your keyboard. Software can bedivided into three basic categories:- Operating systems. These communicate with the hardware of the machine, and actas the basis on which other software programs can be run. The operating system, or OS, isthe means by which both other programs and the user interact with the computer. lt is thefirst thing you see when your computer starts up, and it allows you to tell the computer what itis you want to do. Examples of operating systems include DOS, Windows, UNlX and theMacintosh OS. Operating systems are very important in the story of the PC and we shallPowered by 1/14return to them later.- Languages. These allow developers to write new software programs. There is a widerange of programming languages to suit different types of task; examples include Basic, C,Assembler, Pascal, C++, Visual Basic and Java.You will look at these in detail if you do acomputer programming course, but they do not feature very much in this course.- AppIications. These allow you to perform activities to which the computer is suited.Applications are the reason most people buy computers in the first place. Examples includeword processors (such as Microsoft Word), spreadsheets (e.g. Lotus 1-2-3), databases (e.g.Access), graphics packages (e.g. CorelDRAW), and so on.2: Binary, bits and bytes2007-03-27 16:35 - T171_PCTo appreciate the importance of the various breakthroughs in the history of the computerindustry you will need a basic knowledge of how a computer works, and in this segment youwill look at how a computer represents information. At its very lowest level a computeroperates by turning on or off millions of tiny switches, called transistors. ln computers thesetransistors can only be in one of two states; that is, on or off. Such devices are thus referredto as two-state devices. Another example of a two-state device might be a conventional lightswitch. lt is either on or off, with no intermediate state. The states of 'on' and 'off' can berepresented by the numbers 1 and 0. ln mathematics the term binary is used to refer to anumber system which has only two digits, that is 1 and 0. The number system we use ineveryday life has ten digits, 0 to 9, and is called denary. The binary system is the smallestnumber system that can be used to provide information. Any number from our normal,denary system can be represented in binary; 0 in denary is 0 in binary. Similarly 1 in denaryis 1 in binary. When you get to 2 in denary you have a problem. There are no more symbolsin binary; you are restricted to only 1 and 0. So how do you represent two? This question issimilar to asking how you represent ten in denary. Once you get to nine you have run out ofdigits, so you simply create a new column and start afresh, using 1 and 0. This is also whatyou do in binary, so 2 in denary becomes 10 in binary. When you move on to 3 (in denary)you proceed as before; 3 becomes 11 in binary. The table below shows how denary numbersconvert to binary. Denary number Binary equivalent 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7111 8 1000 9 1001 10 1010 lt is useful to think of binary in terms of columns. The first columnrepresents units, so a 0 here means no units, i.e. 0, and a 1 means 1 unit. The next columnrepresents the numbers of 2s, so a 1 in this column means 2. The next column represents 4sand so on, with each column being twice as big as the previous one. This is also what we doin denary, each column being a factor of 10 bigger than the previous one. So the denarynumber 2902 can be interpreted as (2 x 1000) + (9 x 100) + (0 x 10) + (2 x 1). lf you want toconvert binary numbers to denary, this is a useful method. For instance, if l wanted to convertthe numbers 1000100 and 11001 to denary l would make a set of columns as shown.Powered by 2/14As l mentioned earlier, a computer functions by manipulating 1s and 0s. As you have seen,you can represent any denary number in binary. lt is also possible to represent any letter ofthe alphabet, or other character, using binary by simply assigning a code to it in thecomputer. For instance, there is an agreed representation of text known as lnternationalAlphabet Number 5 (lA-5) in which the letter 'A' is represented by the binary pattern1000001. When l type the letter A, this binary number will be stored in my computer. l canlater retrieve it and the letter A will be displayed on screen. This will only happen if thecomputer has received instructions to treat 1000001 as an lA-5 character. The same patterncould be used to represent the denary number 65. The computer knows what to do with thedata because it has instructions from a program, and these instructions are themselvesbinary representations. lt is worth examining the difference between data and instructions.The data is the current information the computer program is working with. This might besome numbers l am adding up, or some text l am typing. lt will vary from instance toinstance. The instructions are what the computer does with the data. This must always beconsistent, for example clicking on the Save button will always save the data. So numbersand text can be represented using the binary system. What else can? lmages can berepresented using a technique known as bit-mapping. This divides an image up intothousands of cells and allocates a value to each cell. lf the image is in black and white, eachcell will have a value of 1 (indicating it is black) or 0 (indicating it is white). Colour can berepresented by allocating more information to each cell to indicate the proportion of red,green and blue (RGB) values. A wide spectrum of colours can be created by varying therelative values of red, green and blue. What else can be represented in binary? The answeris just about anything. Sound, like images, can be divided up into different segments andeach given an appropriate binary value, which can then faithfully reproduce the sound. Thisis what your music CD player does. You will hear people talk about computers being 'digital'.Sound, light and other natural signals are usually analogue. The difference between digitaland analogue is an important one as it underlies the advantage in using computers for manytasks. You will learn more about what is meant by analogue and digital in the next section.So computers work by manipulating 1s and 0s. These are binary digits, or bits for short.Single bits are too small to be much use, so they are grouped together into units of 8 bits.Each 8-bit unit is called a byte. A byte is the basic unit which is passed around the computer,often in groups. Because of this the number 8 and its multiples have become important incomputing. You will particularly encounter the numbers 8, 16, 32 and 64 in various contextsin computing literature, and this is usually due to the 8-bit byte being the basic building unit.Powered by 3/14The key point to appreciate is that although basing your entire system on only two digits mayseem limiting, these two digits can be used to represent almost anything. You will also hearpeople speak of kilobytes, megabytes and gigabytes or often just 'K', 'meg' and 'gig' as in,'This computer has 64 megs of RAM', or 'This file is 45 K'. Bits, bytes, kilobytes andmegabytes are merely ways of measuring the size of things computers deal with. A kilobyteis 2 to the power of 10 bytes. This is actually 1024 bytes, but is close enough to a thousandto be given the prefix kilo, meaning a thousand. Similarly, a megabyte is 2 to the power of 20(or 1 kilobyte squared), which comes out as 1,048,576 bytes. For the sake of convenience,this is called a megabyte, meaning a million bytes. A gigabyte is 1000 megabytes.3: Analogue and digital2007-03-27 16:35 - T171_PCThe term 'analogue' is often used to distinguish something from 'digital'. For instance, the firstmobile phones were mainly analogue, but there has now been a general shift over to 'digital'phones. The term 'digital' is one which has become increasingly common over the pastdecade or so. lt is used to describe a number of products, such as digital phones, digitalwatches, and digital cameras, among many others. lt is also used as a property ofsomething, as in 'l've got a digital copy of the report'. People also talk of living in the 'digitalage' or of 'being digital'. So what does it mean for something to 'be digital', and why is itgenerally portrayed as a good thing? What does it mean to say something is analogue ordigital? Consider an everyday example - clocks. There are analogue clocks, with hands, anddigital clocks, with number displays. The key features of an analogue clock are that its handscan point to any time on the clock face (on a good clock anyway). The hands sweep throughthe times displayed on the clock face in a continual motion. They do not jump between setvalues. The digital clock, however, is restricted to displaying set numbers. This is the maindifference between analogue and digital: anaIogue signals are continuous, they can take anyvalue within their limits, whereas digital ones can only take set values within their range.DigitaI signals are said to be 'discrete', which means 'separate' or 'distinct'. ('Discrete'meaning separate should not be confused with the commonly used word 'discreet', whichmeans circumspect or prudent.) My Oxford dictionary has the following definition foranalogue: 1. an analogous or parallel thing. 2. (attrib.) (usu. analog) (of a computer orelectronic process) using physical variables, e.g. voltage, weight, or length to representnumbers (cf. DlGlTAL). 'An analogous or parallel thing', where analogous is defined as'partially similar or parallel; showing analogy'. So an analogue object or signal is one which issimilar to its original in its form. For example, the movement of the hands of a clock isanalogous to the passing of time. Definition 2 has it as something which uses 'physicalvariables', which include length, weight and voltage. Note that these are all 'natural' variables,in that they can be found in the natural world (as opposed to the artificial one created by acomputer). Analogue quantities are found commonly in nature. Now let us consider thedictionary definition of digital: 1. of or using a digit or digits... 3. (of a computer) operating ondata represented as a series of usu. binary digits or in similar discrete form. So definition 1has digital as something which uses digits (numbers 0 to 9). This is expanded upon withreference to computers in definition 3, where digital means to operate on data in a binaryPowered by 4/14form. lt also says a 'similar discrete form', which is probably the key difference betweenanalogue and digital. So one of the properties of an analogue signal is that it can take anyvalue within a specified range. A digital signal however is restricted to set values. These arecalled 'discrete' values, since each must be distinct from the other with no overlap. Thealphabet is a good example of a discrete system. ln our alphabet a letter must be one of the26 characters. lt cannot fall somewhere in-between A and B say, it is either A or B. Thiscontrasts with an analogue quantity, such as length. There is an infinite number ofpossibilities that a length can have between 1 centimetre and 2 centimetres. The term digitalis often used to refer to a computer, or a microprocessor, that handles information in a digitalform. ln these cases the digits are usually restricted to just one of two possibilities: 1 or 0.However, natural signals, such as light, sound and electricity, are analogue. lf we are tointeract with digital computers, and use them to act on representations of real things likesounds and pictures, we need a way to convert analogue signals into digital ones. Thisprocess is known as anaIogue-to-digitaI conversion. Digital devices are often faster andmore efficient than analogue equivalents. So why is it that by limiting a system to just twovalues (1 and 0), it is possible to get an improved performance? On the face of it, it wouldseem that an analogue system, which could take any value, would have greater flexibility andpower. There are two main reasons why digital systems are often superior: reliability andmanipulation. ReIiabiIity There is an immediate problem in trying to reproduce an analoguesignal. Since it can take any value, how do you know that the value you have reproduced iscorrect? This problem does not exist with digital signals. Because a digital value can only beone of a set range, it can be reproduced exactly. This is why the telephone network haslargely been switched over to a digital system. An analogue signal declines in strength whenit is sent over a wire, so it has to be boosted (or amplified) at regular intervals. However,when an analogue signal is amplified, any incorrect or corrupted values in the signal (what iscalled noise) is also amplified because it is not possible to distinguish noise from the originalsignal. A digital signal is not amplified, it is regenerated, so the resulting signal is a faithfulcopy of the original. This is possible because of the use of discrete values. Consequentlydigital signals can be sent over any distance you like (provided they are regenerated oftenenough), and the signal received at the end will be as good as the original. ManipuIationAnother reason why digital systems have become popular is related to the increase in speedand power of microprocessors, and their falling prices. Although microprocessors only dealwith 1s and 0s, they do so so quickly and reliably that using a microprocessor to handle thelight input into a camera, say, is now a viable proposition. This means that things can bemanipulated easily. Consider a digital image. lt is represented in a computer as a series of 1sand 0s, which represent the colour, luminescence and hue of each of the image's pictureelements (pixels). lf l have a picture of the British Prime Minister shaking hands with theAmerican President in a digital format, it is not a difficult job to alter it. All l am doing isaltering the 1s and 0s underneath. So, using suitable software, it would not be difficult toreplace the head of the British Prime Minister with my head (taken from a different digitalimage), and blend this in so that it would be very difficult to tell that it was a 'fake'. This wouldbe very difficult to do with an analogue representation, such as an actual photograph. Thisease of manipulation is very important and powerful, and is one of the reasons why workingin a digital format is so attractive.Powered by 5/144: Computer architecture2007-03-27 16:35 - T171_PCln section 3 you saw how a computer could use binary digits (bits) to represent almost anyinformation. This segment will show how a computer uses this binary representation toperform its various tasks. By combining a series of bytes any data or instruction can berepresented. Consider a simple example which takes a number and displays it on the screen.The following instructions might operate for this program: 10000000 = startprogram00000001 = exit program00000011 = consider next byte as a number00000101 =display previous numberThus the following stream of bytes would display 10 (2 indenary):10000000 (program starts)00000011 (it is told to consider the next byte as anumber)00000010 (treated as a number)00000101 (it is told to display the previousnumber)00000001 (it exits) This is essentially what computers do, except on a scale ofcomplexity enormously greater than this. Although computers operate by manipulating 1sand 0s, this is not a very useful way for people to work. A more productive means of tellingthe computer what to do is required. This need led to the development of programminglanguages. The first of these was known as Assembler, which operates at quite a low level inthe computer, telling the computer where to move data and what to do with it. Assemblertakes commands and converts them in to 1s and 0s, which the computer can interpret.Newer programming languages are more sophisticated, and operate at a higher level thanAssembler, and their arrival has made the task of programming simpler. ln the dummyprogram above we used a byte (eight bits) to represent each 'chunk' of information. Mostcomputers now use 32 or 64 bits. These chunks are called words and are the basic units thecomputer manipulates when it is performing an action. The key to your computer is a chipcalled the microprocessor. This is its brains, and is where most of the computing takes place.Before the advent of the microprocessor, computers came mainly in the form of largemainframes which had a different circuit board for each function. At the core of a mainframecomputer are three separate units linked together to form what is known as the centralprocessing unit, or CPU. These three units are:- The arithmetic and logic unit (ALU) - this is the unit which does the actual work of thecomputer. As well as the four basic mathematical functions of addition, subtraction,multiplication and division, it has comparison capabilities such as =, >, < (equals, more than,less than).- The control unit - this unit controls the flow of data from the computer's memory into theALU and to other devices.- The memory. A microprocessor combines the ALU and control unit on one silicon chip,which is why it was at one time referred to as the 'computer on a chip'. ln mainframes theCPU includes memory, but this is separate in microcomputers, so l shall use the term CPU torefer to just the combination of ALU and control unit. l shall describe microprocessors in moredetail later, but you should appreciate for now that they can perform a variety of functions.lnside your computer, in addition to the microprocessor which forms the CPU there are othermicroprocessors that are used to control the graphics card, modem and other devices. TheCPU microprocessor is housed on a circuit board called the motherboard. Also on themotherboard is the cIock chip which acts as a metronome for the computer so that all itsPowered by 6/14actions can be synchronised. There may also be one or two ROM chips. ROM stands forRead Only Memory, which means that the data on these chips cannot be altered, it can onlybe read. These chips often contain some important programs which come supplied with thecomputer and which are needed for it to function properly. This is why they are made to beread-only; it would be very unfortunate if an unsuspecting user altered them. As well as theCPU microprocessor there are devices which can be used to enter data into the computer,and which it can use to output data. These are called input/output devices (usually referred toas I/O devices) and might include a keyboard and mouse (for input) and a monitor andprinter (for output). The data for these devices will often pass via a slot-in circuit board (calleda card) inside the PC which plugs into a slot on the motherboard. These cards perform anumber of functions, such as converting data to a form usable by that particular brand ofdevice. The CPU also sends and receives data to and from the computer's memory, which isusually referred to as RAM (random access memory). The RAM consists of chips similar inconstruction to the CPU. This is the memory which stores all the data the computer iscurrently using. You can think of the RAM as the computer's desk. When it needs to work onsomething it will retrieve it, for example a file from the hard disk, and put it into the RAM - justas you might get a file from a drawer and place it on your desktop. The computer will alsoload into the RAM the programs it needs to work with this file, in the same way you mightplace your calculator on your desktop. Like a desktop there is a limit to how much can beplaced in the RAM. The contents of RAM are often lost when the computer is switched off.The microprocessor will also have to read from and write to a permanent data storage devicein the form of a hard disk drive. Other permanent storage devices include CD-ROMs (againthe ROM in the name indicates that these CDs cannot be written to), optical disks, tapestorage or fIoppy disks (which may be read only or writable). To receive and send all of thisdata the microprocessor is connected to cables, which are referred to as buses. This termcomes from the Latin omnibus, meaning 'for all'. Buses are designed to carry all kinds ofdata, rather like the buses you might use to travel around a city (their name is also derivedfrom omnibus). Thinking of your computer as a street layout, with traffic and busestransporting data to various destinations, is not a bad way of visualising what is actuallyhappening. This is a simple overview of a computer's architecture, but it is sufficient for thiscourse. The architecture is summarised in the figure below.Powered by 7/145: Computer power2007-03-27 16:35 - T171_PCPeople often talk about the power of a computer. What do they mean by this and whatfactors affect it? So what influences the speed and complexity of the computer? There areseveral factors. The first factor is the microprocessor chip used for the CPU. Successivegenerations of chips have more and more transistors placed on them. With more transistorsavailable the chip can be programmed to perform more tasks, therefore increasing itscomplexity. lncreased numbers of transistors also allow the chip manufacturers to implementnew methods of improving memory usage and speed of performance. For example, earlierversions of the lntel microprocessors required a separate chip to be installed in order to copewith any software requiring lots of complex calculations. The extra chip, known as a mathsco-processor, was integrated in the main microprocessor as more transistors were madeavailable in subsequent versions. Such improvements in successive generations ofmicroprocessors are typical, and are made possible by the increased numbers of transistorsavailable. The second factor that determines a computer's power is its clock speed. Eachaction of the CPU can be thought of as occupying one cycle - although most modern CPUscan perform several tasks at the same time. Therefore the greater the number of cycles persecond, the faster the computer.Powered by 8/14The third factor is the size of the words that both the microprocessor and the buses canaccommodate (go back to the previous segment on computer architecture if you need torefresh your memory about these). You may sometimes hear people refer to a computer - orparticularly a games console - as a 32-bit, 64-bit or 128-bit machine. These terms refer to thesize of word that the microprocessor can manipulate. The larger the word size, the moreinformation each word can contain. A 32-bit word can contain twice the data of a 16-bit word.Therefore increasing the word size improves both the complexity (more data can bemanipulated) and the speed (because it takes the same time to interpret each word). A fourthfactor that affects a computer's power is the amount of memory, or RAM, available. RAM actsas the computer's working memory, so it contains the information the computer needs for itscurrent session. This will include various operating system commands (e.g. what a mousedouble click means), the programs currently running (e.g. Microsoft Word with twodocuments open), current display configurations (e.g. that one Word document is in front ofthe other and the mouse pointer is in the top left of the screen) and so forth. An increase inthe size of the RAM increases the amount of data it can store at any one time. This improvesthe complexity of the computer because it can run programs that require a lot of data to behandled, and several programs can be run simultaneously. lt also increases the speed of thecomputer because when the RAM becomes full the computer will temporarily store data onthe hard disk. This will be retrieved when it is required, which takes more time than having itcurrently available in memory. So more RAM provides more speed.Powered by 9/14The power of computers now is such that their performance is fast enough to meet mostneeds, and the software you use does not really necessitate the rapid upgrade it once did.This gradual easing of demand poses a problem for the computer industry.6: Types of computer2007-03-27 16:35 - T171_PCThe most commonly available type of computers are based on microprocessors. These arecalled microcomputers or personaI computers (PCs). There are other types of computerthough, and you might like to be aware of these. However, don't get too bogged down in thedetails - the important thing is that you have an appreciation of the different types ofcomputers and the tasks they might perform.Mainframes were the dominant form of computing before microcomputers. They are usuallyvery expensive, powerful and operate specialist software. Mainframes are typically used bylarge companies, public authorities and universities for their data handling tasks. These tasksare typically:- File maintenance: This is perhaps the most common use of mainframes. Maintainingrecords is a huge task for institutions. Records can contain information on sales, credit cardstatus, payroll details, social security details, health records, stock inventory, etc. ThesePowered by 10/14either need to be accessed by different people in real-time (for instance a travel agentbooking an airline ticket) or updated in batches (for instance warehouse stock levels at theend of each day). lt is necessary in such cases to have the data stored centrally and thenaccessible by those who need it. A lot of minicomputers are now capable of performing thesetasks in medium-sized companies.- Simulations: Many physical and engineering problems cannot be solved without thehelp of complex computer simulations. These require intensive mathematical work, and sotake advantage of a mainframe's computational power. Examples include weatherforecasting, or calculating the position of astronomical bodies with extreme accuracy. Manyminicomputers or workstations are now used for this type of problem.- General purpose: Many universities used a mainframe to act as a general purposecomputing facility. Each user can then be given their own area on the mainframe to storefiles, and different departments can use its resources to perform different tasks, e.g.predicting bird populations in the Biology department and calculating metal stress in theEngineering Department. PCs are now used to perform many of these tasks. You will havenoticed that after each task l mentioned that other types of computer could now be foundperforming these tasks. This indicates that the general growth in the mainframe area hasslowed and is even in decline, as smaller computers have become more powerful.Mainframes are still required by many institutions, however, to perform large data handlingtasks. They are particularly useful when data needs to be held centrally, with different peopleneeding access to it. This is illustrated below:Minicomputers are powerful, special-purpose computers. They were originally viewed assmall mainframes - hence the prefix 'mini'. However, they have become increasingly powerfuland have replaced mainframes for many functions. Examples include Digital Equipment'sVAX machines and lBM's AS/400s. Tasks minicomputers might be used for include:- Plant control: Many industrial plants require a central computing facility to collect datafrom various sensors and then to act accordingly. For example, in a chemical engineeringPowered by 11/14plant, as the pressure in one vat increases the computer registers this, and opens a releasevalve slightly while also adjusting the boiler temperature.- Network control: Many computer networks need a central computer which providesstorage space and controls the network using special network software. This is known as aserver. The other computers which access the server are called clients. Such machines canalso act as the interface to the lnternet, accepting lnternet messages and hosting e-mail andWorld Wide Web facilities. Powerful PCs can also be used to perform these functions.- Databases: As mentioned above, the role of mainframes in file maintenance isincreasingly being taken by minicomputers. Minicomputers can hold databases of recordswhich appropriate people can access. For the general public it is PCs which tend tosymbolise computers. However, most 'heavy duty' computing is performed not by PCs but byminicomputers. With the growth in networking computers in most institutions the role ofminicomputers has grown. lt is in this market that some of the largest software companies,such as Novell who provide networking software and Oracle who supply database software,do most of their business. The network model is shown below.Workstations are based on specialised microprocessors and can be thought of as powerfulPCs. They are typically used for specialist engineering tasks. Workstations use a special typeof microprocessor known as a RISC (reduced instruction set computer) chip. Thistechnology, developed at lBM, removes many of the complex instructions from amicroprocessor and has instead a set of basic instructions, which perform their tasks veryquickly. This approach increases the speed and the power of the microprocessor, particularlywhen dealing with numerical problems. The workstation market is dominated by SUNMicrosystems. They typically cost in the 10,000s, and can cost 100,000s. Tasksworkstations might be used for include:- CAD/CAM: Computer Aided Design and Computer Aided Manufacturing have beengrowth industries since the mid-1980s. These technologies allow engineers to designPowered by 12/14complex machine parts without having to produce an actual physical model. The necessarycomplex, 3-D graphics require a lot of computing power and good quality video capabilities.- Animation: Similarly to CAD/CAM, animations require a lot of processing power whichmust be performed quickly, and are ideally suited to the RlSC technology.- Simulations: Performing simulations of processes, such as the behaviour of anindustrial plant, requires considerable computing power.- Multitask programming: Any complex programming which is deemed to require morepower than is offered by a PC, and which needs to perform more than one task at a time(called multitasking), is often performed on a workstation. Recent PC operating systems suchas Windows NT can also perform multitasking. The workstation will typically be part of anetwork. Microcomputers are based on a microprocessor and are intended for individual use;hence they are called personal computers, or PCs. They were initially standalone machines,but are increasingly connected to a network. They are ideal for tasks such as those listedbelow where the user requires individual computing power.- Word processing: Word processing programs allow a user to produceprofessional-looking documents, with different fonts, styles and pictures. The production ofcomplex and attractive documents is much easier with the use of word processing softwarethan it was in the days of the typewriter.- Spreadsheets: Spreadsheets allow a user to create mathematical models. These areparticularly useful in financial planning and can be used to answer questions such as 'Whathappens if we raise the cost of our product by 1%?'.- Desktop pubIishing: This allows people to create drawings, manipulate images andcombine them with text to produce professional graphic design work, for instance magazinelayouts, posters, book covers, etc.- Games: Although this may seem a non-serious use of computers, games represent alarge market. By making use of the PC's computing power very good quality graphics andcomplex game play can be achieved.- Servers: As mentioned above, many powerful PCs are now being used as servers tocontrol a network. Generally the tasks performed by the mainframes have been taken overby minicomputers. PCs initially created a new type of usage for the computer; for instance,spreadsheets and desktop publishing took over from activities previously performed by hand.As PCs have increased in power they have begun to be used for some of the tasks thatrequired minicomputers and even mainframes in the past. With the increase in computerpower the distinction between types of computers is often difficult to maintain. When does aPC become a workstation for instance? Remember, though, that having an appreciation ofthe different types of computers and the tasks required of them is important, but you shouldnot get too bogged down in trying to categorise machines.7: Summary2007-03-27 16:35 - T171_PCPowered by 13/14ln this Unit you have covered some of the basic principles of how a computer operates, andwhat its various components do. You have also met some of the terminology used in theindustry. ln this Unit you have covered:- What software and hardware are.- The different categories of software.- What binary is, and how it relates to denary.- How a computer uses bits to represent information.- What analogue and digital mean.- The main components of a computer and their functions.- The factors that affect the power of a computer.- The difference between mainframes, minis, workstations and PCs.- Computer terminology, such as RAM, ROM, CPU, bytes, kilobytes, data, instructions,l/O, motherboard, buses and words.Powered by 14/14