Welcome to the first edition of a new column looking into the practicallities of Personal Computers, better known these days as PCs. I shall be concentrating on the IBM compatible PC in its various forms. This is the dominant type of personal computer, though I am not denigrating the products of the likes of Acorn, Apple, Atari or Commodore. These may be fine machines but cannot be considered to be the mainstream systems. With a user-base of millions of machines in the UK alone, and still growing steadily, the IBM compatible PC is now very much a part of everyday life for their owners.

I intend to provide in these columns some straightforward explanations of PC jargon and brush away as much of the mystique as possible. Bear in mind that most of the users of the PCs do not have very much idea about what goes on inside the box but still get very successful results from them. All that is needed is enough information to make the purchase and use of a PC as painless, even enjoyable, as possible

Many PC users find their machines to be excellent for running a variety of games on. Although I cannot comment on the attraction or play-value of any games, I shall try to explain which factors in the specification of a PC affect the running of a game. So if it is your intention to play games on a PC you will know what to look for on the back of the game pack when it says "Minimum system requirements".

ALL THOSE NUMBERS!

Let's make a start by looking at the CPU. The what? The Central Processing Unit. It's at the core of any computer and is the starting point for any description of a particular PC. So, for instance, a PC might be described as a 486 or a 286, but what meaning does that convey?

When the PC was first released by IBM it used a CPU called an Intel 8088 to do its processing - that's as close to "thinking" as a computer gets. Many manufacturers copied this basic design. When chip-maker Intel introduced the 80286, IBM and the others modified their design to take advantage of the increased processing power offered by the 80286, or 286 for short. Later the 386 was introduced, followed by - you guessed - the 486. As of 1996, the 486 is the mainstream type of PC even though later designs of CPU are now available. Intel refrained from calling the follow-up to the 486 the 586, instead they called it the Pentium, for copyrighting reasons. The next, and most recent, generation in this long line of development is called the Pentium-Pro.

As a general rule-of-thumb, each generation of CPU is about twice as powerful as its predecessor, the upshot being an increase in speed in getting results to the user. But beware! There are different speeds made of each of the CPUs mentioned and this will, of course, reflect in the speed of the PC. I shall move on to a discussion of CPU speed and how to interpret the speed figures quoted in the next PC Corner.

ANY QUESTIONS?

My aim is to provide the information which is of most use to readers so let me know via the editorial office if there are any issues you want covered.

Welcome to the second edition of our monthly feature on Personal Computers (PCs). Last time I described the numbering scheme used to describe the main differences between computers such as the 286 and the 486. This time I'll break down these differences even more and describe the different CPU speeds found in PCs.

More Numbers (and Letters!)

When the 386 was first introduced the CPU (the 386 chip itself) was the most expensive single component in the computer. To cut down costs Intel, the chip manufacturer, introduced a cut down version called the SX. This had all the internal circuitry of the original 386 but externally it was more like the older 286. But the basic processing power was there so the 386SX was only slightly slower in operation than the 386. At about this time they also introduced the 80387 which is known as a Maths Co-processor. Some computer programs are able to do mathematical operations quicker if they are run on a PC which has the Maths Co-processor fitted.

As we know, the next CPU to be introduced was the 486, and here the lettering system differed slightly. From the outset it existed in two versions - the SX and the DX. This time, the 486SX was the standard 486 processor, there being no difference between its internal operation and its external connections. The 486DX was an enhanced version which included a Maths Co-processor inside the 486 chip.

Speed Thrills!

CPU speed is quoted in megahertz, abbreviated as MHz. The original IBM PC CPU speed (also known as clock speed) was 4.77 MHz. Recent CPUs have a clock speed of 133 MHz and set to rise even higher. In between are the PCs likely to be used by you and me! 286s were made with speeds of 8, 10 or 12 MHz, 386s used 16, 25 and 33 MHz, and 486s have 25, 33, 50, 66, 80, 100 and 120 MHz clocks. Pentiums run at 60, 90, 100 133 MHz and so it goes on........

To describe the 386 and 486 chips in the most succinct way, all the numbers and letters described above are run together, giving such catchy titles as 386SX33 and 486DX50. Just one, final, complication before I close this month. Another variation on the 486DX numbering comes in the form of the 486DX2-66, the 486DX2-80, the 486DX4-100 and the 486DX4-120. The number after the DX is concerned with how the clock speed is used when it gets inside the CPU chip. For our purposes the only significant number is the final one - the 66, 80 etc which are the clock speeds.

And Finally....

A final word before we all feel inadequate about the clock speed of our PCs. The very high speeds mentioned above are provided for rapid response times when running the most recent, very complex programs which many of us will never see. For the straightforward applications most of us will run, such as word-processors and spreadsheets, a "slow" PC will do just fine and other factors such as memory and Hard Disks are of more significance. More on these things another time. But in the meantime, don't forget I'll gladly answer PC related questions in these columns. Just send them in via the editorial office. 'Till next time.

Welcome to this month's look into the world of PCs. Previously we have seen how the different CPUs relate to each other and how the speed of each affects the performance of a PC. Most of that was a pretty dry subject so this month we'll take a look at the lighter side of using PCs and concentrate (not too hard!) on how they look on the screen.

Operating the System

All computers have software called the Operating System. It's normally held on the Hard Disk but may be built into chips on the PC's circuit boards or it may be loaded up from floppy disks. The job of the Operating System is to make the PC's resources available to your applications (such as Word Processors) in such a way that they do not spoil programs and data required by other applications. Because most of the resources being kept under control are in the form of accessing the computer's disks, the Operating System is, more specifically, the Disk Operating System, or DOS.

Think of DOS as a protective layer over the nasty bits and pieces which make up the PC. Underneath the layer are the machine resources. On top of the layer is the interaction between DOS and you, the user.

Communicating with the machine is now a matter of communicating with DOS, and normally that involves typing in words and abbreviations at the keyboard and viewing the results on the screen. Bear in mind that, so far, I am only talking about controlling the machine. Communicating with the application depends on the application itself.

GUI, gooee!

In the early 1980s, the firm of Xerox in the USA conducted some development work based on the assumption that computer users would find computers more productive if they had a more user-friendly interaction with their machine. They believed that remembering odd sequences of letters and numbers hinders the use of the PC and that providing on-screen menus with a form of visual display of the machine would be easier to use. They added to this an input device for pointing and clicking to remove much of the need for the keyboard. That work led on to the development of the Apple Macintosh computer and, for IBM-compatible PC users, the Windows Graphical User Interface (GUI).

Windows in its various forms now dominates the world of PC applications. One of the main benefits Windows has brought has been nicknamed WYSIWYG - pronounced wizzee-wig! It stands for What You See Is What You Get. It means that the image displayed on the screen is very close to how the image would appear when sent to a printer. More on Windows and what it provides next time. In the meantime....

A Question

A question has flooded in concerning upgrading from a Commodore Amiga to a PC. A lady has asked me if the games she uses on her Amiga can be used on the PC if she upgrades to a PC. Sadly, the answer is "no". Even though both machines can use the same size of floppy disk (3.5"), the format of the information is different and, even worse, the computer program to run the game is entirely different. The reason behind this problem is that the Amiga does not use a CPU chip which is compatible with the Intel chips we discussed in the first PC Corner. So, in a nutshell, any programs required for the new machine must be ones specifically written for the IBM-compatible PC. Luckily, there are thousands of them!

And now a question for you. Is there any topic you would like covered in PC Corner? Let me know via the editorial office. So, until next time, Happy PCing!

Hello again. Last time I introduced Microsoft Windows as a way to make using a PC more "user-friendly". Although not compulsory for controlling Windows, a "mouse" is, I feel, essential for making Windows as user-friendly as possible. It can also be used to control many non-Windows programs.

A Mouse in the House

When you are using Windows there is a pointer on the screen which is normally in the shape of an arrow. The mouse is used to move the pointer around the screen. The action is a bit like using a joystick on a computer game. Moving the mouse away from you moves the pointer up the screen, moving it towards you moves the arrow down the screen and side to side movements are similarly controlled.

A mouse has one, two or three buttons on its top surface, just where your fingers rest. Most commonly there are two buttons, and the right-hand button is not used very much. Controlling an action by using the mouse involves pressing a button - normally the left-hand one - when the pointer is in the required position on the monitor screen. Sometimes the button is pressed once, sometimes twice in rapid succession and sometimes, rarely, three times in rapid succession. A further control done by the mouse is called "drag and drop" which means pressing and holding the button, moving the mouse to a new position and then letting go of the button.

These basic features of using a mouse are all that is required to control your applications when using Windows. You can start programs this way, save your work on a disk, draw shapes in a graphics-drawing program, change the shape of the actual "windows" on your screen and much more. Naturally a certain amount of keyboard use is required when numbers and letters need to be typed in but most of the control features are taken care of by using the mouse.

Looking into Windows

Windows has gone through several generations - the original version we can call Windows-1, then came Windows-2, Windows-3 and finally (so far!) Windows-95. There were also smaller variations within each of these main Windows versions.

One of the first things you notice about using Windows is the little pictures which are meant to represent something the computer can do for you. These little pictures are called "icons". As an example, this column was written using the very straightforward Word-Processor program which comes with Windows and is called Write. The icon for Write is a little picture showing the nib end of a fountain pen drawing a letter A. To start up the Write word-processor I had several options when using Windows but a common way to do so is to double-click the mouse button whilst the screen pointer is over the Write icon.

Some of the other programs to use which come built in with Windows are a Calculator, a computerised card-file system for holding names and addresses and a clock which can be visible on the screen even when other Windows programs are being used. Each of these has its own icon - a picture of a pocket calculator, a stack of card-file cards and a small clock respectively. Starting them off is just the same as with Write, namely double clicking the mouse when the pointer is over the icon.

There'll be more on Windows and how to control its facilities next time. But for now, I'll leave you with the usual invitation to send any questions in for me to answer. Bye for now.

Hello! Welcome to this month's PC feature.

I have previously described WIndows as a layer over the DOS operating system which make using the PC more intuitive. It adds user-friendliness to using the programs or "applications" which you are running. Windows comes with several applications of its own so I thought I would give a summary of these before moving on.

Things you get with Windows

Write Write is a Word-Processor program. It is ideal for writing letters and reports but lacks the features of more advanced word-processors. It can select different character sizes and shapes (fonts) and allows you to show them as italic, underlined or bold. You can also line up the text to the left, to the right or have it centred. You can also Justify the text so that both the left-hand-side and the right-hand-side are straight edges. The sort of features you would get with a more advanced word-processor are spell-check, printing into a number of columns, newspaper style, and the use of Templates, which give you a standard format for each type of document you create.

Paintbrush Paintbrush is a graphics designing program. When you start up Paintbrush you see a set of "tools" on the left-hand-side and a choice of colours along the bottom. There is also a box for selecting the line-width. The tools allow you to draw lines, circles, rectangles etc using the mouse to move around the screen. Shapes you create can be filled with different colours or patterns such as a brick-work effect and the outlines can be whatever colour you select. If you are using a black-and-white printer these colours are interpreted as different shades of grey. Having created a picture it can be copied into a word-processor document if you like by using Edit-Copy in Paintbrush followed by Edit-Paste in Write.

Terminal The program Terminal is provided to make the whole Windows-PC operate like a Visual Display Unit (VDU). This can be useful if you want to connect up to a remote computer system such as a Bulletin Board using a Modem and a telephone line.

Calculator If you pop-up the Calculator it looks just like a picture of a normal hand-held pocket calculator. You press the buttons using the mouse and the digits are displayed as you enter them and as the result of the calculation is produced. The display can even be copied into a document to save having to copy the numbers out. If a standard calculator doesn't have enough facilities for you there is a Scientific Calculator option - selecting Scientific from the View menu makes the calculator "grow" giving you scientific features like Sine and Squareroot as well as mathematical features like Hexadecimal numbering.

Well, I seem to have taken up enough of your time and the magazine's space for one month! Next time I'll give you a brief description of Windows' Calendar, Cardfile and Clock as well as covering Character Map, Media Player, Notepad, Recorder and Sound Recorder. Any questions - you know where to send them....

Welcome to the PC feature and, as promised, I'm covering a few more of the Applications which come built-in as part of Windows. Don't forget you can add extra applications which are designed to operate with Windows and use the same methods of control as Windows itself.

Windows Calendar

The calendar icon looks like a pair of open pages from a diary. But when you start up Calendar it doesn't just tell you today's date. What this program does is allows you to keep a full appointment-booking system on your computer. When you open a particular page for a particular date you can type in your appointments for various times throughout the day. There is even a facility for setting an alarm and this can go off 10 minutes early or just on-time. When the alarm goes off it pops-up a little display window and, optionally, makes a sound.

Who hasn't forgotten an important anniversary? Well you can mark special dates in Windows Calendar using different symbols for different types of special day - but you still need to go out and get the card yourself (unless of course you print you own from Paintbrush!....)

Cardfile

This program produces a simple database for you where you can save, for instance, people's names, addresses and 'phone numbers or any other information which needs organising like perhaps details of your record collection. It operates like a database because you can tell the program to search through all the items you have entered and it will give you all the details for that item. When you use Cardfile it appears on the screen like a set of index cards. The details you store on the card are whatever is useful to you but they needn't just be ordinary text, you can place a picture created in Paintbrush on each "card".

Clock

The Windows Clock can be used to show the time on screen as either a normal clock face or in digital format. When used in digital format it also shows the date. When you start the clock it gets the time from the system settings which are part of the PC so you don't have to tell it the time when you start it. Because the clock doesn't interfere with anything else you might be doing on the computer you can leave it running whilst doing other jobs like word-processing.

Character Map

The Character Map can be very useful to insert non-standard characters into a document. For instance you might want to insert the character for the Japanese currency, the Yen. That character doesn't appear on the keyboard but it can still be put in the document by finding it in the Character Map and doing a COPY - PASTE operation.

Media Player

This application allows you to control audio and video facilities using the screen and the mouse. If your PC has a CD-Rom drive attached you can make it play audio CDs with Media Player. It can also control Video Disks and MIDI musical instruments. If you have some digitised sound files on your hard disk you can make the sounds come out of speakers if you have a soundcard.

Notepad

Notepad is a text editor. It is used for making changes to some of the text files used by the system. Of course if you also do computer programming on your PC it can also be used to write programs and edit them. It differs from a word-processing program like Write in that the text doesn't fit itself into the page width automatically - each line would go on forever if you let it! (Forever is an exageration, by the way). Another difference is that there is no formatting information associated with the text such as bold lettering, italics, different fonts and so on.

Sound Recorder

If you have a sound card in your PC you can make your own files of digitised sound using Sound Recorder. But Sound Recorder is also used to play existing sound files which exist on your hard disk. You can recognise these files because they end in .wav which is short for wave. Windows comes with some of these files and they can be played through the speaker in the PC instead of through a soundcard. This requires the addition of some software which is called a driver.

Windows uses drivers for many purposes such as for sending data to a printer or for controlling the mouse. If you have any questions on drivers or any other topic please send them in via the editor. Until next time then I'll say bye for now.

A Case Study

This month I shall start to describe an exercise I went through recently for one of my relatives. He wanted a PC but of course there were cost constraints. Could I obtain or build something suitable? I shall spend a couple of "PC Corners" on this in order to go into a useful amount of detail.

The System Requirements

My relative has little interest in games, the main use of the PC being word-processing. It should also be capable of running a decent drawing package and, ideally, an encyclopaedia such as Encarta. Finally, it should be upgradeable and stay reasonably up to date for a few years.

The System Basics

Together, the encyclopaedia and upgrade requirements dictated that no less than a 486 would do. Furthermore, such modern equipment is normally easier to set up than earlier designs. To hold an advanced word-processor, the drawing package and the program to run the encyclopaedia would require a hard disk drive of about 100Meg. A CD-ROM drive would be needed to hold the encyclodeadia disk itself and about 4 Meg of RAM would be a good start for the work required. The monitor type would need to be VGA to display pictures from the encyclopaedia - SVGA could be a later upgrade.

Getting Started

The starting point for a project like this is the motherboard, otherwise known as the main board. The motherboard is the board which most of the rest of the PC parts plug into. The memory, in the form of SIMMs, plugs into the motherboard, as does the 486 CPU and the keyboard. There are also slots in it for plugging in the display card and the controller cards for the hard disk drive, the floppy disk drive and the CD-ROM drive. The connectors for a printer and a mouse are normally provided by the disk controller card.

A decent secondhand motherboard made by Pine was bought at a computer fair, together with a 50 MHz 486 CPU. As it happens, the motherboard can be upgraded to hold a Pentium-class CPU. There are 8 memory slots available, each of which can hold a 30-pin SIMM. Now the latest motherboards use 72-pin SIMMs but it was felt that 30-pin SIMMs will be available for many years so this limitation didn't seem to be important.

As I had the relative with me at the time we also chose an attractive case to hold the motherboard and all the cards. PC cases come with power-supplies and the connections are common to most motherboards. These days, you even find that the fixing holes line up!

Building Work

The first step was to test the purchases - ideally while the computer fair is still running! I had 1 Meg of RAM spare so I plugged that in - it used up 4 of the 8 memory slots. I connected up the monitor and display card from my own PC as well as the keyboard and switched on, powering the whole assembly from the newly- bought PC case's power supply.

These tests showed that all was well so far. I was able to enter the BIOS (Basic Input/Output System) and setup the display type and memory capacity in the battery- backed up on-board memory. This is special memory which is part of the motherboard. It is used to store information which must not disappear even when the PC is switched off.

I'll stop there for this month and describe how all the other bits and pieces went together next time. Bye for now.

Welcome to the PC feature and, as promised, the second part of the Case Study of the construction of a PC for one of my relatives.

The Story So Far...

I bought a case with power-supply and a motherboard to go in it. Using some spare parts, I tested these purchases so I was ready to proceed to the next stage.

More Building Work

The motherboard is held in the case with some nylon mounting pillars and a couple of screws. The screws are particular to PCs so it's just as well they came with the case. However, the mounting pillars were not provided so I had to use some recovered from an old defunct IBM. I temporarily plugged-in a couple of adaptor cards to make sure it lined up at the back of the case and screwed the motherboard in.

More Parts Required

Most of these were bought new but luckily the most expensive parts, the hard disk, the CD-ROM drive, the memory and the monitor were available secondhand.These items become available from time to time as people upgrade their computers from say 130 Meg hard disk to 540 Meg, or their monitor from VGA to Super-VGA. I bought 4 Meg of RAM memory and added that to the 1 Meg I had used for tests giving a very respectable 5 Meg for the finished system.

I used mail-order to get the floppy-disk drive, the controller card (Super-I/O: it includes the printer connection and the mouse connection), the CD-ROM interface card, the keyboard and the mouse.

Assembly

I fitted the 3 drives (CD-ROM, Hard disk, floppy disk) into the case and plugged in the Super-I/O card and then realised I'd forgotten the display card. So it was off to the next computer fair and a basic VGA card bought for a tenner or so. I had some of the internal interconnection cables already and the ones I didn't have I made up myself.

Testing, Testing

The basic functioning of the system is fairly easy to test - certainly the PC seemed fast and reliable. There are several test programs available called benchmarks which run through all the features of a PC and give you an actual numeric answer as to how your PC is performing. I used one of these programs, a PC magazine cover-disk actually, and it confirmed that the PC was running well.

What next?

Well, nothing is needed because the PC goes well. But the benchmark program suggests improvements in areas it calls "bottleneck". A minor bottleneck on this machine is the amount of RAM and an increase to 8 Meg will give an improvement in performance at some time in the future. However, my relative prefers the idea of more facilities so will probably go for a sound card and a bigger hard disk to hold more programs and data before increasing the RAM.

Until next time then I'll say bye for now.

Hello and welcome to this month's PC feature.

This time I'm going to talk about printers. To many people, the printer is the link from the computer to the real world. Having carefully word-processed that important letter, somehow you've got to get it into an envelope!

General Printer Types

The first printers which gave well-formed (so-called "letter-quality") characters were daisy wheel printers. Each character is on a separate "petal" of the daisy-wheel and a hammer presses it onto the paper, through an ink-ribbon, working on a similar principle to a typewriter. Daisy wheel printers are not used much these days as they are noisy, can be slow, won't print graphics and changing the character shape necessitates changing the actual daisy wheel.

Dot matrix printers are inexpensive, can usually print graphics and will print different character fonts under software control. They are normally either 9 pin or 24 pin, the latter giving very clear sharp characters and graphics. Even a 9 pin dot matrix printer will print graphics and different fonts. They also have the advantage of printing through several sheets of paper at once, like a typist uses carbon paper.

An ink-jet printer squirts a tiny blob of ink onto the paper at precisely the right instant and so builds up an image of graphics or text. The resolution is very good, especially if the best quality paper is used. However, the ink cartridges are more expensive than the ribbons used by dot matrix printers and the ink can be washed off with some models. They cannot print through several layers of paper, either. As an economical way of achieving excellent print quality they are probably the most popular type for domestic users at present.

For the best quality printing, a laser printer is the ultimate. They give the sharpest images in both character fonts and graphics. They use separate sheets of paper where the others can use separate sheets or continuous paper. Running costs are less than ink-jet printers - some use a cartridge which needs to be replaced when it runs out, others use the cheaper alternative of using refills. Unlike most ink-jets, the print is bonded to the paper and won't wash off. It uses similar technology to a photocopier

A BIT of Theory

Attaching the printer to the computer is usually done by either a Serial data connection or a Parallel data connection. All computer signals take the value ONE or ZERO - it's the so-called Binary numbering system. One signal element is called a BIT, which is short for Binary DigIT. When the computer is told to send characters to the printer it typically sends 8 bits to describe a particular number or letter or to represent a particular pattern of dots for the printer to print. With a serial data connection these 8 bits are sent one after the other. With a parallel data connection the bits are sent 8 at a time. So you need more wires for a parallel connection than you do with a serial connection. Normally the PC's serial connection is on a 9 way connector and the parallel connection has a 25 way connector.

Why waste all those extra wires for a parallel connection? Well most printers use parallel connection because the set-up conditions are easier and because less electronics is needed at the printer end.

Well, I seem to have taken up enough of your time and the magazine's space for one month! If you have any questions - you know where to send them....

Bye-bye for now.

Hello again - time for another PC feature

Rodents

The topic this time is the humble mouse. There are several different types and they sometimes cause problems so I'll try to explain what these differences can mean to you.

Buttons

A mouse for a PC generally has two buttons but sometimes there are three. The middle button is used by few programs; the left button is the most used. This is the button for selecting drop-down menus, highlighting words and so on. The right button is used by some programs for bringing up a pop-up menu anywhere on the screen. If it suits you better, the left and right button functions can be swapped over in Windows Control Panel.

Types of Mouse

The different types of mouse which might be required by your computer are mainly differences in the connection details. The plug on the end of the mouse lead can be one of three types and the actual signals can also be one of three types. Just to add to the confusion, some types of mouse can employ two of the signals! Let me explain further.

The three types of mouse are the serial mouse, the bus mouse and the PS/2 mouse. The serial mouse is the most common these days and it plugs into the COM (1 or 2) connector on the PC using a 9 way D type plug. The PS/2 mouse is the second most common and attaches to the PC with a mini-DIN plug. Now some brands of mouse will work as either a serial mouse or a PS/2 mouse. Obviously an adaptor plug is needed to match the connector on your PC but that is not all. The mouse itself either has a switch underneath or it automatically detects which type of mouse your PC is expecting.

A bus mouse has a connector a bit like the mini-DIN so I'd better try to describe how you tell them apart. Both are about 8mm across but the 6 pins of the mini-DIN are arranged in a circle with a plastic lug taking up a 7th position. The pins on a bus-mouse connector are arranged in a grid pattern.

The actual connector on the computer is generally part of the motherboard but, in the case of the bus mouse, may be on a plug-in adaptor. Where a serial mouse is concerned the connector may be part of the I/O (Input/Output) plug-in card. The connector is sometimes a 25 way connector so an adaptor would be needed for the 9 way connector on the mouse lead.

Software

One of the clever aspects of Windows is that, whatever mouse is plugged in, the software will automatically detect it and use the mouse which is connected. But do not be tempted to plug-in or unplug a mouse with the computer switched on - the mouse or the computer may be damaged and the software already running will almost certainly fail to recognise the mouse until the system has been re- booted.

If the mouse is going to be used from DOS it will be necessary to point to the mouse-driver software in the start-up files. The mouse driver is normally part of DOS but if not it comes on a disk with the mouse itself.

Choosing a Mouse

Only a user can decide what shape of mouse he or she finds comfortable, but do bear in mind reliability. If the buttons feel well made and have a definite feel to them then it should be a well-made mouse. With prices ranging from £10 to £50 or more it is worth spending a while choosing.

The computer itself may have some limitation which dictates which of the 3 mouse types should be bought. For instance, if the computer has only 2 COM ports (this is usual) and if you are using the 2 COM ports for a modem and a printer, say, then connecting to a PS/2 port on the motherboard or plugging in a bus mouse adaptor may be the best option.

Well, I hope this information on our little non-furry friends helps. If you have any questions then please contact the editorial office. 'Til next time then, bye-bye for now.

Hello and welcome to the PC feature. This time I'm going to run through a case-study - someone had problems which needed sorting out.

A case of unreliable operation

A reader of this column (THE reader of this column....!?) contacted me about her errant PC. The mouse was failing to respond and errors were being reported in reading and writing to C: (the hard disk drive). The PC was used mainly for word-processing but all documents were saved on floppy disk rather than hard disk. Now the floppy disk drive is drive A: so the errors in accessing C: were puzzling to the user.

The reason the PC was accessing the hard disk drive were twofold. Firstly, the application being used, the word-processor, is held on the hard disk so as different facilities within the application are needed the PC has to load in different program modules from time to time. Under normal circumstances this is completely transparent to the user. The second reason for the hard disk drive accesses is that most Windows applications keep a backup copy of the work in progress in a directory (TEMP) on the hard disk. This is so that you have more chance of recovering your work if the power goes off suddenly, but my advice is that you do not rely upon this, and save regularly.

I had a look at the PC at home and found out a few things about it before carrying on. It was a 386 running DOS version 6.1 and Windows version 3.1 (Windows 3.11 requires a 486). The hard disk had a 40 Meg capacity and appeared to be of the type known as MFM. However, without looking up the spec it isn't possible to tell whether or not it might be the slightly later type known as RLL. The drive had its own controller board inside the PC. The floppy disk drive also had its own controller board. There was a third board, the I/O (input/output) board, for the mouse, on a serial port, for the printer, also on a serial port, for a parallel port (unused) and a games port, also unused.

Suspecting that some of these facilities might be clashing with each other, I unplugged the I/O board and fitted a separate bus-mouse card and a separate serial card. There is a DOS program called MSD, MicroSoft Diagnostics, which tells you about the PC's ports, controllers, memory etc so I ran that program and it still recognised a games port! This was not required but could have been clashing with the one I unplugged so I left the I/O board unplugged and proceeded with the rest of the testing.

I looked at the values stored in the CMOS memory. This is a special area of the PC's memory which holds its values even when the power is switched off, thanks to a little battery on the main board of the PC. The values for the hard disk looked more appropriate to an RLL drive rather than an MFM drive but I didn't have time to check the scecs so I had to leave the values alone. In any case, changing the CMOS values would certainly have resulted in the loss of data on the disk.

Another useful pair of programs in DOS are DEFRAG and SCANDISK. I ran scandisk to check for errors in the filing structure on the hard disk and did a surface scan to check if the internal recording medium of the disk was sound. Both of these were OK so I ran defrag. This program brings together on the disk all the parts of the files which belong together and brings together all the spare space on the disk. This can speed up the operation of the drive slightly, especially when it's getting close to full. These two DOS programs are useful preventative maintenance for anyone running DOS. Windows 95 and Windows NT do it automatically because they don't run "on top" of DOS.

Back to the story..... Defrag reported a large area of unmovable blocks in the middle of the drive. This added to my suspicions about the CMOS values but time was marching on and the PC was needed urgently! It operated reliably now and correcting the hard drive set-up could wait for another day. When the PC isn't needed for a few days I shall copy all the data onto floppy disks, look up the hard disk drive parameters and copy them into the CMOS. I can then reformat the drive and hopefully free up its full capacity.

All of this happened a few weeks ago and I trust the PC is still performing OK! If you have any queries please let me know. 'Til next time, then, bye-bye.

Hello again. Time for a bit more description of some of the bits and pieces that go into a PC. In particular, that useful built-in or add-on component known as a CD-ROM drive.

CD-ROMs and CD-ROM Drives

First then, an explanation of its name. CD is simply an abbreviation of Compact Disk. That's right, it's the same as a music Compact Disk. In fact the technology is the same and therefore economical. The Disk is just the same but contains data files like a floppy disk instead of sounds.

The ROM bit is rather more complex. It stands for Read-Only Memory. This means that the data on the disk can only be read from the disk by the PC, you cannot write data from the PC onto the disk. At least that's how they started - now there are versions which can be written to.

So the CD-ROM is the disk itself - the device which reads it is the drive. Now the CD-ROM drive can be mounted either in the PC itself or externally in its own box. The real issue is, once again, the connection details.

CD-ROM Drive connections

The commonest type of connection for a CD-ROM drive these days is called IDE. It stands for Integrated Drive Electronics, but the important thing is that it's the same as the connection for a hard disk drive. Many hard disk controller cards have a second IDE connection for adding a CD-ROM drive. However, it IS possible to connect an IDE CD-ROM drive to the same connection as the existing hard drive but performance may be a little slower.

Other types of connection exist - proprietary, that is named after the manufacturer, and SCSI, pronounced scuzzy, which stands for Small Computer System Interface which is a high performance connection suitable for many devices like scanners and hard disks, as well as CD-ROMs. The proprietary connections are: Sony, Mitsumi and Panasonic so if you want to fit one of these manufacturers' drives and it uses the manufacturers own interface you need that type of interface on your CD-ROM controller card. It's not as bad as it sounds! - many sound cards, for instance, have both IDE and proprietary connections on the board.

Internal or External

Most people have the CD-ROM drive mounted internally but there are instances where an external drive is more suitable, such as for a portable computer. The two usual connections for external use are the SCSI connection (usually called the SCSI-bus) and the printer, that is, parallel, port. This may seem strange but it can be quite fast and the problem of having to disconnect the printer is not important because a special adaptor is used to give you the CD- ROM connection and the printer as well, so you don't lose the printing facility.

Speed - again!

Speed always seems to be the question-mark when specifying components for the PC. Of course CD-ROM drives are specified by speed as well. They started by running at the highest speed that an audio CD runs at. As an aside, an audio CD doesn't run at a constant speed like a gramophone record, it runs at constant linear velicity - so it has to speed up when playing tracks near the centre. I just thought you might like to know that!

Then came 2x speed CD-ROM drives, and rapidly (!) speeds up to 12x, 16x or even 20x. The slowest and therefore cheapest currently on the market are probably the 4x and 6x drives but I would expect even these high performance drives of a couple of years ago to become obsolescent in a year or so. Such is progress..... The message as always is, though, if the equipment is up to the job you want it to do it is by definition good enough.

More on PCs and associated topics next time, but in the meantime, if you would like to browse old issues of PC Corner and you have access to the Internet, you can find them (careful over upper and lower case letters) at:

http://geocities.datacellar.net/Hollywood/Academy/1557/

and follow the links to PC Corner. Bye for now.