Computer Systems. Objectives. Chapter 5

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1 Computer Systems Chapter 5 A computer system consists of various elements; each of these has a specific function. In this chapter you will be given a general overview of how the parts of a computer system fit together and what role each plays in assisting you with your work. Objectives In this section you will cover: Various types of computers The main parts of a computer Input devices Output devices Central processing unit Storage and memory Units of storage Storage devices Software o Applications o Utilities o Programming o Operating systems o The graphical user interface. Microstar Publishing Pty Ltd

2 Use Business Technology Types of Computer Systems There are various types of computer systems. The most commonly used and recognised computer system is the PC. Many people now have a computer in their home. Larger organisations use progressively more powerful computers. Details on each type of computer are outlined below. Microcomputers are usually known as a personal or home computer. Microcomputers are now commonly used in homes, schools and businesses. A new microcomputer generally costs around $2000 for a basic model up to $4000 for a system with extra features. Minicomputers can do more than microcomputers. They cost more, do more and store more information. More than one person can use them at the same time because they usually have several terminals connected to the server of the minicomputer system. They are used in medium sized organisations and for departmental use in large organisations. Main Frames are used in large organisations such as retail corporations, telephone companies and universities, where large amounts of data are to be processed and stored. Main frames can cost hundreds of thousands of dollars but they work very quickly. Many terminals are connected to the main frame. These terminals may be in the same building, the building next door or another state. 5-2 Microstar Publishing Pty Ltd 2004

3 Computer Systems 5 Computer Hardware No matter what the size of a computer system they all still have the following components. 1. Device for Input of Data 2. Memory for Data and Information Storage 3. Central Unit for Processing of Data 4. Device for Output of Information The power of a computer lies in its ability to store and process data. However the computer must have a way of getting the data into the computer. Devices such as the keyboard and mouse are used to input data. Once the data is input it is stored in various types of memory until it is required. There are primary and secondary storage areas. A computer can also manipulate the information, such as presenting it in various ways or performing calculations. A computer can only do these things because of programs located on the system unit. A program is just a set of instructions to the computer on what to do with the data we input. The resulting information can be output using devices such as the screen and the printer. The input and output devices are often called peripherals. Output -Monitor - VDU Output - Printer Processing - System Unit Storage Hard Disk Input - Keyboard Input - Mouse Microstar Publishing Pty Ltd

4 Use Business Technology Hardware: Input Technology Below is a list of the more common input devices. While reading about them consider if you have seen the device in use or places where it could be used. Keyboard the most commonly used input device is based on pressing keys to enter characters into a document and to perform some functions in a program. Scanner - usually a flat bed device, will scan data such as photos and text into machine code which can then be stored and manipulated. Barcode Reader commonly used in supermarkets and retail stores, works by passing a laser light over a barcode a series of lines which represent a code light is reflected which inputs the code, and hence data, about the item being scanned. Mouse another commonly used device particularly in the home PC and the office PC. The mouse controls the position of the cursor on the screen and determines selections and some actions. Touch Sensitive Screen will input the users choice based on the point on the screen that the user touches. Most appropriate for a relatively small number of choices per screen, 12 or less, and when high precision is not required. Digital camera replaces the traditional camera will input and store images which can then be transferred to a computer for processing. Optical Mark Recognition Reader will scan documents such as questionnaires and tests for specific marks such as a tick or a cross. Magnetic Ink Character Recognition Reader (MICR) will read numbers printed at the base of a cheque or similar document used widely and predominantly in the banking industry. A MICR reader can process over a thousand cheques per minute reading the cheque details. Speech Recognition a microphone is used to record the speech which is converted to text using appropriate software and then displayed on a screen. Commands can also be spoken which will move the cursor around the text. 5-4 Microstar Publishing Pty Ltd 2004

5 Computer Systems 5 Hardware: Output Technology Information can be output as either hard copy, such as a printed document, or soft copy on a screen. Printer produces a hard copy of the information as characters and graphic images on paper or similar medium. Plotter produces a hard copy - will produce special prints of technical drawings, maps, design etc. These are very precise. Screen produces a softcopy - will display the program in use and the contents of the file being retrieved or manipulated. Speech synthesizer produces sound - will convert text into speech with the use of an appropriate program. Speakers will output audio such as music, instructions, warning signals. Hardware: Central Processing Unit The Central Processing Unit (CPU) is central to the workings of a computer. The CPU controls the movement of data between devices and directs how and when the other devices work together to perform processing and storage tasks. The CPU still relies on an initial program to start it and the addition of other programs so it will perform required tasks. Microstar Publishing Pty Ltd

6 Use Business Technology Hardware: Memory and Storage The computer system must have some way of storing data, information and programs. Some common methods of storage that you may have heard of are floppy disks and CDs. Building Blocks of Memory There are various types of memory devices but they are all based on bits. A bit is the smallest unit of storage. BIT One bit is the smallest unit. It is the building block of all pieces of data. The term bit is derived from the term Binary Digit. BYTE A byte is a group of either 8, 16 or 32 bits. Memory on the computer is divided into bytes. Each character stored uses about one byte of memory. So the word elephant would use about 8 bytes. 1 Kilobyte is about 1000 Bytes 1 Megabyte is about 1000 Kilobytes 1 Gigobyte is about 1000 Megabytes 1 Terabyte is about 1000 Gigobytes Primary Storage Primary storage is the term given to internal memory that will temporarily store the data and information, and program instructions while they are in use. It is located within the Central Processing Unit. RAM and ROM are the two main types of Primary storage. ROM - Read Only Memory. The computer can read information that is stored here as the name suggests, Read only also means other information cannot be stored here, ie it is one-way. The information stored in ROM is input as it is being manufactured. It is not possible to change or delete this information. It generally holds the information required to start the computer. The information is stored here regardless of power supply. RAM - Random Access Memory. This is the memory used while processing is in progress. It is a two way memory in that it both stores and recalls data at any time as long as there is a power supply. Once the power supply is turned off any data in the RAM is lost unless it has been stored on another secondary storage device, more about this on the next page. The RAM stores the operating system, any application currently being used and the data required for that application. 5-6 Microstar Publishing Pty Ltd 2004

7 Computer Systems 5 Secondary Storage Secondary storage is for permanent storage of data and information. It does not rely on a power supply as it uses magnetic or sometimes optical systems to store data. This enables a computer to be turned off but data retained for use at a later date. It also stores programs that are not in use. Secondary storage is capbale of storing enormously larger quantities than primary storage. Once other portable methods of storage are used the amount of storage is unlimited. There are various secondary storage devices. Floppy Disk commonly the 3.5 inch disk which holds 1.44 megabytes (MB). It is easily transportable from one computer to another and is also useful for backups of small files or installing programs. Super Disk also 3.5 inch disk but holds 120 MB. Very similar in appearance to a floppy but a bit thicker. Relies on software to run and also a suitable drive attached to machine. Which makes it less portable but still a great way to store large amounts data. Disk Cartridge often know by the popular brand name Zip disk will hold either 100 MB or 250 MB. Hard Disk will store generally between 20 to 60 Gigabytes on the home/office PC to up to a Terabyte on larger mainframe computers in large organisations. The hard disk or disk drive is really just a collection of disks similar to a stack of CDs. Data or Information stored here can be retrieved at any time from any location this is called random access. It is similar to the ability to pick out a track on a CD without first playing the preceeding tracks. It is permanently located within the unit unlike the others which are all portable. External Hard Disks - are becoming very popular as way of transporting large amounts of data. Capacity can vary and cost increases with capacity but is generally more expensive than the equivalent capacity in an internal hard disk. Magnetic Tape Can store about 500 megabytes. While it is slow, it is also cheap and the large amount of data it can store is useful of backing up a hard drive. When compared to a music cassette they are wider, thicker and of higher quality. However they are similar in that the whole tape must be played until the particular data is located. This is called sequential access. It is a much slower way of accessing data compared to the random access in disk drives. Microstar Publishing Pty Ltd

8 Use Business Technology CD ROM Can store about 650 megabytes permanently. Primarily used as a permanent source of a program. It is often used to store video tutorials and large books such as encyclopaedias. CD-R and CD-RW Writable CDs are a cheap alternative to superdisks. The CD-R is a write once read many medium while the CD-RW can be erased and new data saved, similar to a disk. The CD can be expensive, but the writable CDs are cheap. DVD (Digital Versatile Disk) holds over four gigabytes of data including sound and audio. A DVD drive connects to a computer in way similar to CD ROMS. However the disk can be double sided and even two layers with double sides giving a total of 17 Gigabytes. Because of their size DVDs can be used to store full length movies. Smart Card Has the look of a credit card but it houses a microprocessor that will record financial transactions. The smart card is loaded with a specific amount of money which is reduced each time it is used. A Phone Card is a good example. You might buy a $5 phone card. Each time you use it the microprocessor records the transaction and reduces the available balance until all funds are depleted. Computer Exercise 1 1. What is primary memory? 2. What is the main difference between ROM and RAM? 3. What is secondary memory? 4. What are the main differences between hard and floppy disks? 5. What is the difference between a CD and a DVD? 6. Find out how much each of the following devices cost. Also find out the price of a single disk or cartridge used in the device. Zip Drive CD Burner DVD Burner 5-8 Microstar Publishing Pty Ltd 2004

9 Computer Systems 5 Computer Software So far we have talked about Hardware in a system. The Hardware will only work as well as the programs that coordinate it to process the data to become information. The software cannot actually be seen. You can see the result of using the program on the screen. You can see the CD or disk it is stored on but you cannot see the actual program. There are four main categories of software in a computer system. System software Utility software Application software Programming languages System software System software makes the computer run. This includes the operating system. Common operating systems are Windows 98 or XP, Linux and Mac OS. Utility software These programs are maintenance type programs that are used to keep the computer running smoothly. They are important for the efficient organisation of files. File processes such as Copy, Move, Delete, Backup etc of files are carried out in these programs. Windows Explorer, Windows Disk Defragmenter and Microsoft Backup are some commonly used Utility software programs. Application software Application software determines how the data is processed to produce information. For example, Microsoft Word, Lotus Notes, Corel Draw etc. Programming languages Programming languages are used to produce custom applications. Languages such as BASIC, Fortran, COBOL, Visual Basic etc. Microstar Publishing Pty Ltd

10 Use Business Technology What is an Operating System? A computer s Operating System is a system program or programs that control the operations of a computer. The operating system determines how each hardware component of the computer system is used. The operating system enables us to print a document while at the same time opening a file or entering text. The operating system also provides an interface between the user and the programs. The interface sometimes known as the Graphical User Interface makes the computer much more user friendly. Windows is a commonly used operating system because all programs that work in Windows while having various functions have the same Windows qualities. For example when you see Word for Windows or this program written for Windows, these labels are indicating that these programs have the Windows features. The name Windows is appropriate because the Windows program allows us to look through windows at the work we are doing in various programs. For example we may have a word processing program such as Microsoft Word and a spreadsheet such as Microsoft Excel running at the same time. We can use Windows to move from one program to the other quickly, or even view both at the same time. The Microsoft Windows program has made working on computers much easier and more efficient. Computer Exercise 2 1. What is the difference between hardware and software? 2. On the computer you use: Which operating system software does it use? List two applications available for you to use? 5-10 Microstar Publishing Pty Ltd 2004

11 Computer Systems 5 Office Equipment: Care and Consumables There are many different types of office technology. The following is a general discussion on caring for the more common pieces of office technology. Please keep in mind that it is general as each type and make of equipment will have specific procedures required for that particular piece. Keyboards Keeping the keyboard as clean as possible is important. Keep fluids and food away, and use a dust cover when not in use. Dust and food build up around the keys can cause them to stick and either make it difficult to enter a character or the opposite, enter too many characters each time the key is pushed. Mouse For a long time a mouse worked by way of a ball within the mouse moving to indicate where to move the pointer on the screen. This ball often collects dust particles which can build up on the rollers that surround the mouse to detect movement. This dust should be regularly cleaned out so the mouse continues to move smoothly. Check the instructions for your mouse on how best to clean it. Printers Generally printers use either toner or ink to produce the image on the paper. It is important to have a supply of replacement ink or toner cartridges for when the cartridge currently in use runs out. Many printers will now indicate when the cartridge is getting low in toner or ink. You should always have a replacement in the office as a supplier may not always have one on hand for your immediate purchase. Also printer cartridges are very specific to the printer, so ensure you purchase the correct one. In caring for the printer you should ensure that connections are secure to promote correct data transfer from the computer to the printer. A printer will generally have a maximum amount of paper that can be inserted in the paper tray. Also if you are using recycled paper ensure that it is not stapled forcing the whole stapled wad to move through the printer when printing. I have seen a printer rendered useless by this type of accident. Once again a dust cover should be placed over the printer when not in use to prevent dust build up around working parts. Microstar Publishing Pty Ltd

12 Use Business Technology Scanners Check the Instruction book on how best to care for the scanner. Take care that leads are connected properly. The scanner glass should be cleaned periodically with an appropriate cleaner to maintain a high quality image. The glass can become soiled by scanning documents or items that themselves are dusty, have ink spots or simply dirty. The glass should also be protected from knocks and metal, as any scratch on the glass will be a permanent inclusion in any scanning. Cleaning the scanner glass To clean the scanner you should disconnect the power chord from the scanner, then open the scanner lid You should use a soft lint-free cloth with a mild glass cleaner. Avoid abrasives, acetone, benzene and carbon tetrachloride, all of which can damage the scanner glass. Avoid isopropyl alcohol because it leaves streaks on the glass. The safest course is to use a cleaner recommended by the manufacturer. Dry the scanner glass with a clean soft lint-free cloth When dry, reconnect the power cord to the scanner NOTE: Fingerprints or smudges under the glass do not affect the appearance of scanned images as they are outside the range of focus for the scanner Microstar Publishing Pty Ltd 2004

13 Computer Systems 5 Digital camera Caring for the Camera Storing the camera. Digital cameras can be stored as any digital equipment however the following conditions should be avoided Direct sunlight High humidity Extreme dust Close proximity to air conditioner, heater, or moisturizer Inside a hot car Areas of high vibration Proximity to explosive materials Cleaning the camera: The best quality photos are produced when the camera is kept clean: Cleaning the body: Wipe the entire surface of the camera using a clean, dry, soft cloth. Cleaning the camera lens: It is especially important to keep the lens clean as dust particles can show up as dots on photos. Use a blower to eliminate dust. Use a lens cleaning tissue to wipe off the lens if necessary. Avoiding Condensation Condensation can occur if a digital camera is subjected to sharp temperature changes, which can create sufficient condensation to cause damage. To alleviate these conditions when in a cold outdoor environment, the camera should be carried close to your person. NOTE: Should condensation occur, remove the batteries, and leave the battery door open for several hours. Microstar Publishing Pty Ltd

14 Use Business Technology Digital Camera Consumables There are two elements that are consumed in a digital camera, the battery and the memory card that stores the pictures. Memory A digital camera is sold with usually 8 or 16 megabytes of memory. About 15 to 20 pictures can be taken with 8 megabytes. The safest way of ensuring that you will have enough memory for a photo taking session is to download you photos at the end of each session. That way you will sure that there is a maximum amount of memory available. Alternatively you can purchase additional memory cards, and large memory cards if you find you need to take more photos in each session. The Batteries The state of the battery is important. A digital camera uses a lot of energy when taking a picture. Some cameras simply replace the battery while others rely on the battery being recharged in a manner similar to a mobile phone. Each make and type of camera will have specific requirements. The following is general information. You should always read the manufacturers instructions for maintaining your digital camera. There are generally two types of batteries used in digital cameras, replaceable batteries and rechargeable batteries. Utilise the following tips to prolong the life of your batteries. Do not recharge batteries until they are fully depleted Limit the use of the LCD screen on the battery (displays the photo taken) it is better for the battery to actually view the picture after downloading or on a card reader if one is available. Limit the use of the zoom feature by considering what type of photo is usually taken and setting the zoom for that distance. Turning the camera off immediately a picture is taken will save the life of the battery. If possible use an AC Adapter if available and practical. For example when downloading images to the PC. You may wish to consider the wealth of battery information posted on the Web at Microstar Publishing Pty Ltd 2004

15 Computer Systems 5 Maintenance of Office Technology When all else fails read the instructions. Many people try to start using pieces of equipment without reading the instructions. They base their efforts on other equipment they have used before or just hope for the best. These days with so many different varieties of equipment it is very important to READ THE INSTRUCTIONS and follow them. In doing so you can prevent damage to equipment and in the long run your use of it will be much more efficient. In caring for office equipment the following should occur 1 Designated staff should be assigned role of caring for equipment and given appropriate training 2 All staff should receive adequate training in the use of equipment according to the manufacturer s guidelines to a prevent misuse and possible damage to the equipment b enable them to identify problems and register them for attention by designated staff c identify correct consumables required 3 Consumables should be replaced as required to a level determined by office standards 4 A maintenance program should be developed for: a regularly checking equipment according to manufacturer s care instructions for each individual item b In-house cleaning and servicing of equipment according to manufacturer s guidelines should occur at determined intervals c Periodic servicing by qualified or manufacturer approved technician 5 A log book should be used to record a detected faults b subsequent action or repairs c periodic maintenance and inspections Microstar Publishing Pty Ltd

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