Back to Basics - Summing Up

To end our back to basics series I want to bring you on a photo tour of the inside of a PC, pointing out some of the items we discussed during the course of this series. Remember, to see any picture in more detail just click on it.

First up and overall view of the PC we will be looking at with its side panel removed. For those who weren't paying attention, the rear of the PC is on the left!

Moving in in more detail, the next picture shows the heatsink fitted to the CPU. The actual CPU can't be seen in the picture because the heatsink is mounted on top of it. The heatsink used on this PC is a low-noise type made of copper and aluminium made into a series of radial blades that present a large surface area for heat transfer. The large, low-speed fan in the centre of the heatsink only comes on when the CPU exceeds a certain temperature. Because this particular heatsink is very efficient at dispersing heat on its own, the fan remains off most of the time, leading to a quieter PC.

The next picture shows the memory modules mounted in the motherboard memory slots. This motherboard has four memory slots (2 x purple and 2 x orange) and two of the slots are occupied with 512MB of DDR2 RAM in each, for a total of 1GB of RAM.

Now we're looking at the PCI slots on the motherboard, of which there are five. The slot above the first PCI slot is the AGP slot and contains an AGP graphics card. Moving downwards, the first PCI slot is unoccupied. The next one down contains a TV tuner card. The third slot is unoccupied while the fourth slot contains a wireless network card. The final slot is empty. Just because there are five PCI slots on a motherboard, it does not always mean that you can use all five of them. For example, because of the large heatsink on the graphics card in the AGP slot, there is little room for fitting a card into the first PCI slot.

The hard disc shown in this picture is a relatively recent type referred to as a parallel type, as opposed to the older and more common serial type. The principal difference between them is the connectors. Rather than using the wide ribbon data cables I discussed in the section on hard disc drives, the unit shown in the picture uses a smaller and more easily fitted parallel cable (red in the picture). The other difference is the power connector which isn't the typical Molex type but a slimmer design. Otherwise the hard disc drive types are indistinguishable and the disc is mounted in its usual position at the bottom front of the system case.

This PC is fitted with a single optical drive, a CD-RW unit, located at the top front of the system case. In the picture you can see the multi-strand ribbon cable attached to the drive (this is a special type of ribbon cable rolled into yellow tubing to take up less space in the system case) as well as the 12V Molex power connector.



The power supply unit, or PSU) is fitted to the top rear of the system case and in the picture you can see part of the wiring loom that comes out of this unit. The following picture shows where the ATX power connector fits onto the corresponding socket on the motherboard.















Finally, a picture of the back of the case that shows, from the top down, the rear of the PSU (in brown), the on-board connectors that are built in to the motherboard (these are the mouse and keyboard PS/2 connectors, 2 x serial port and 1 x parallel port connectors, 4 x USB ports, an ethernet port and 3 audio sockets for loudspeakers and microphone). Click on the picture to see a larger version. Note that I didn't deal with the parallel and serial ports in my earlier articles as these are used less and less (if you have an old printer you may still be using the parallel port - sometimes called the printer port).

To the right of the on-board connectors is one of the system case fans, which exhausts warm air from the case.

The bottom section is where the connectors from the AGP graphics card and PCI cards emerge into the world.

So, there you have it. Hopefully, if you have been following our Back to Basics series from the beginning, you now have a better understanding of the different components that come together to make your PC work.

Back to Basics - The Power Supply Unit

The power supply unit, or PSU, is what provides power at various different voltages to the motherboard and other components inside the system case. The size and type of connections attached to the wiring loom comply with the ATX standard so that, physically at least, any PSU can be mounted in any ATX system case. The PSU is always mounted at the top rear of the system case and will normally have at least one fan that serves two functions: it vents warm air from the system case that arises from the CPU heatsink; it cools the PSU itself, which can generate quite a bit of heat when a full load is being pulled on it.

When the PSU is mounted in the system case the back panel of the PSU protrudes to reveal the standard mains kettle lead connector and, on some models, an on-off switch. There is usually also a voltage selector switch which should always be set at 230V for the Irish supply. Mounting and dismounting the PSU in the system case is via four screws on the back panel.

There are two connectors that connect directly to the motherboard - these are the ATX power connector and the 12V power connector (see pictures). Both these connectors are keyed, which means that they cannot be inserted incorrectly into the motherboard sockets. The PSU provides power at a number of different voltages: +12V, -12V, +5V, -5V and +3.3V each of which is supplied to the motherboard via the ATX connector. The accompanying pin-out diagram displays the voltages associated with each pin of the ATX connector.

In addition to the ATX connector and 12V power connector, both of which are plugged directly into the motherboard, the PSU has two other types of connector (well it actually has more, but the others are outside the scope of this article) and these are the 12V Molex connector, which is used to bring power to the optical drives and hard disc drives, and the 12V floppy disc connector, both of which can be seen in the accompanying photo.

The output of a PSU is measured in Watts and PC manufacturers have had a tendency to put in PSUs with low-ish power ratings (150-200W). That's not a problem until you start adding extra components to your PC, which increases the overall power consumption. This can happen if you add an extra hard disc drive, or install a more up to date graphics card. If you exceed the overall power rating of your PSU you may find that the PC randomly crashes or reboots. The problem can be readily rectified by upgrading the PSU to say 250-300W. You should be aware that you can now buy PSUs rated at up to 700W - but bigger is not always better. It's been estimated that even the most heavily loaded PC running full bore will not exceed 300W, so going for a PSU that delivers over twice that amount of power may just result in extra heat being generated, requiring extra fans for cooling, resulting in a noisier PC.

To finish up this series I'll bring you on a tour of the innards of one of PC Medic's PCs that will show all of the items mentioned in our Back to Basics articles in situ in a real PC.

Back to Basics - Optical Drives

The term "optical drives" is a fancy collective term for CD-ROM , CD-RW, DVD-ROM and DVD-RW units which can be found in practically all PCs these days. Let's just clarify the definitions: CD-ROM will allow you to read CDs only but not write to them; CD-RW, will allow you to read and write to CDs; DVD-ROM will allow you to read both CDs and DVDs; DVD-RW will allow you to read and write both CDs and DVDs. If you are unsure what type of device, or devices, you have on your PC you can check by going into the Device Manager, expanding the entry for DVD/CD ROM drives and looking at the properties for each entry.

The CD and DVD units that fit into your PC are a standardised size to fit in the 5.25" bays found at the top of the system case. The picture shows how it looks before mounting in the system case. There are three connections on the back end of the unit: a ribbon cable that connects to the motherboard, identical to the one that connects the hard disc drive; a 12V Molex power connector that comes from the power supply unit which powers the motor that spins the discs; an audio lead that connects to the sound card or sound module on the motherboard (without this you will hear system sounds and sounds in games, but not music from CDs).

Just a couple of points in relation to CD and DVD units.

1. If you want to record music CDs that you will play on other CD players, such as in a car or home CD player, don't use CD-RW (rewritable) discs. While these will normally replay fine on the CD drive that they were recorded on, they don't always play on other units. Stick to CD-R (recordable) discs.

2. To be able to play DVDs on your PC you need to have a video codec (compressor/decompressor) installed, which is a piece of software produced by companies like nVidia or Intervideo. Chances are that such a codec was installed on your PC when you purchased it. However, if you ever have to reinstall your operating system don't be surprised if you can't play DVDs. Windows XP does not natively support DVD playback and you will have to install a third party codec - either one that came on the discs supplied by your PC manufacturer, or you will have to purchase a third party codec.

3. Don't be cheap when buying CD and DVD recordable media. From my own experience I can tell you that if you buy no-brand, "50 for €10.99" discs you should be prepared to end up with a lot of coasters. Cheap media often do not play back well on any unit but the one that they were recorded on - stick with a good brand like Verbatim, Imation or Traxdata.

While it isn't an optical drive, I want to say a few brief words about floppy disc drives in this section as they don't warrant a section to themselves. The floppy disc drive, if you have one, and you probably do, is attached to the FDD connector on the motherboard by a ribbon cable and it has its own power connector that comes from the power supply unit (see the pictures).

In the 21st Century, nobody should still be depending on floppy discs for backing up their data. Modern day floppy discs are notoriously unreliable as they are being manufactured too cheaply to assure quality. PC Medic has found that up to 30% of discs bought at retail level cannot be written to and many of those that can be written to cannot be read at a later date. Do not put your trust in floppy discs - use more reliable methods such as CD or USB memory sticks. You have been warned.

Next ... the PSU.

Back to Basics - Plug-In Cards

We mentioned in our earlier article on motherboards that modern motherboards can have most of the functionality needed integrated into the on-board electronics, such as modems, networks cards, graphics cards, etc. While this is certainly true, many PCs use motherboards that do not have this functionality integrated. So what happens if you decide to use your PC on a home network but find that there is no network interface built into the PC? The answer is that you fit a network interface card to one of the empty PCI slots on your motherboard (refer back to the motherboard article to see what these slots look like). The PCI slots in motherboards allow plug-in cards to be inserted and these can then communicate with the rest of the PC. In order for this to happen device drivers must be installed, but we'll come back to them in a moment.

The picture on the left shows a variety of different plug-in cards that can be added to the motherboard to enhance the functionality of the PC. From the top down we have a modem card, a graphics card, a sound card and a 10/100 network interface card. With the exception of the graphics card, these all can be fitted to any free PCI slot on the motherboard (most motherboards have between 3 and 5 PCI slots). The graphics card is plugged into a special dedicated graphics slot called the AGP (advanced graphics port) slot, of which there is ever only one on a motherboard. Other PCI slot plug-in cards that could be fitted include TV tuner cards, USB connector cards, wireless network cards and Firewire cards. As there are a limited number of PCI slots on your motherboard, and some of them may already be occupied, you may not be able to fit all of the options just listed.

If you bought your PC in the last 12 months you may have a new type of PCI slot called a PCI Express slot in addition to, or instead of, standard PCI slots. These new slots use a different architecture which allows data to transfer at significantly higher rates than the older PCI slots and will eventually replace the older slots on all new motherboards. The PCI and PCI Express slots are a different physical design and cards designed for one slot type cannot be used on the other.

Just inserting a plug-in card in a slot is not enough to allow the card to start operating with the rest of the hardware and the operating system. In order to get the card talking to the other hardware and the OS it is usually necessary to install what are known as device drivers. A device driver is a software program written for a specific piece of hardware that allows it to communicate with the rest of the system. Drivers can sometimes become corrupted and when that happens the hardware that the driver was written for can malfunction. This can normally be remedied by the removal of the corrupted driver followed by a reinstall of the driver. Often manufacturers of plug-in cards release their products to market before their drivers have been fully debugged and problems can arise when using the hardware under certain situations. Because of this it is not uncommon for the manufacturers to release updated drivers that address known issues as they come to light. Windows XP makes it easy to update drivers as new versions are released.

Of all the various types of plug-in cards that are available, adding or upgrading a graphics card is probably the commonest, particularly if a PC is being used for playing games. When it comes to adding a new graphics card, the sky is the limit in terms of how much you can spend. The card on the left is a recently released XFX GeForce 7900GTX graphics card for playing the latest and next generation of games. This will set you back a cool €650 - more than you might pay for a new PC system from Dell. For the dedicated gamer only!

Next up, optical drives.

Back to Basics - The Hard Disc Drive

Whereas RAM can be said to be the equivalent to short-term memory, the hard disc drive (or HDD) can be thought of as the long term memory of the computer. Every PC has a least one HDD and its becoming increasingly common for home PCs to have a second one. Hard disc drives come in two form factors - 3.5" drives and 2.5" drives. The larger drives are used almost exclusively in desktop PCs of the type found in homes and offices, while the smaller 2.5" drives are found in laptop computers. The pictures above show a 3.5" HDD (left) alongside the smaller and thinner 2.5" HDD. In a desktop PC the HDD is normally mounted in an enclosure at the bottom of the system case and will be connected to the motherboard by means of a ribbon cable similar to the one in the diagram. Also connected to the HDD will be a 12V Molex power connector from the system power supply unit. A closer look inside the HDD case will reveal why a 12V power supply is needed.

Inside the case, which you should never attempt to open, is a stack of circular platters. These are made either of aluminium alloy or a mixture of glass and ceramic. To allow data storage, both sides of each platter are coated with a magnetic medium - formerly magnetic oxide, but now, almost exclusively, a layer of metal called a thin-film medium. This stores data in magnetic patterns, with each platter capable of storing a billion or so bits of data per square inch (bpsi) of platter surface. Typically two or three or more platters are stacked on top of each other with a common spindle that turns the whole assembly at several thousand revolutions per minute. There's a gap between the platters, making room for magnetic read/write heads, mounted on the end of an actuator arm. The designation 3.5" and 2.5" refers to the diameter of the platters. The 12V power supply is needed to turn the spindle at speeds up to 10,000 rpm, but more commonly 7,200 rpm.

Because the HDD has platters rotating at such high speeds and a read-write head zooming around just above the surface of the platters, it is easy to damage a HDD if the PC is moved or jolted suddenly while the platters are spinning.

As we said at the beginning, the HDD is the long term memory of the PC where programs, data and indeed the operating system itself are stored as magnetically-oriented metal particles on the surface of the platters. This data is persistent and, unlike the data in RAM, does not disappear when power to the PC is turned off. The amount of data that can be stored on a single HDD has grown dramatically over the past few years. Five years ago a 40GB hard disc drive was considered large. Today, the largest capacity HDDs are in the region of 500GB and most new PCs will have 160GB-250GB HDDs as standard - an awesome amount of storage capacity for a domestic PC.

Tomorrow, plug-in cards.

Back to Basics - RAM

RAM, or random access memory, is your computers short term memory. It should not be confused with the hard disc, which provides long term storage space for programs and data. When you turn on your computer the information needed by your operating system (Windows) to get the computer up and running is loaded into RAM. When you decide to launch a program, such as a word processor, that program is loaded into RAM and it remains there for as long as the program is being used. If you want to open further programs, these too will occupy a part of the available RAM. As the amount of RAM on any computer is finite, if you open too many programs you will find that you will start to run out of memory, everything will start to slow down and your computer will start to feel unresponsive.

You should remember that RAM only stores information when your computer is turned on - as soon as you switch off your machine all information in RAM is lost.

So what does RAM look like. The most common type of RAM in most home PCs is DDR DIMM RAM - quite a collection of acronyms that stands for double data rate, dual in-line memory module, random access memory. This type of RAM comes on modules like the one in the picture.

RAM modules come in different sizes and the capacity of a module is measured in bytes (a byte allows eight bits (or individual binary numbers) to be stored. Typical modules allow between 64MB (megabytes, or million bytes) and 1GB (gigabytes, or 1000 million bytes). These modules plug directly into the motherboard and most motherboards have slots for between two and four RAM modules. In general, most modern PCs can be fitted with between 512MB and 4GB of RAM. Unfortunately, in order to keep their retail price low, many computer manufacturers used to skimp on the amount of memory that they fitted to their PCs. This is particularly true for PCs that are more than 2-3 years old.

So, how much memory do you need. Quick answer? As much as you can afford! Adding memory to a memory deficient machine is probably the most cost effective upgrade that you can make. If you are running Windows XP then, in our opinion, you should have at least 512MB of RAM. Yes, you can run XP with just 128MB, but as soon as you open more than one application things will start to slow down. With 256MB things improve somewhat, but you will still have slow downs if you are using more than three or four applications or if you have many memory-resident applications running in your system tray (icons in the bottom left of your screen). Depending on the particular PC that you have, 512MB of RAM can be added for between €80-€100 and this can transform a sluggish 3-4 year old machine into a perky one that will meet needs for another few years.

If memory fails it can manifest itself in a number of ways, but random reboots is one of the most common. If your machine tends to reboot for no particular reason while you are using it then faulty RAM is a prime suspect (though there are other possible causes). Another fault that is seen with RAM is module creep, where the module gradually creeps out of the connector. This arises due to the heat/cold cycling of the module and can result in a completely dead machine that refuses to boot. So check for looses RAM modules if your machine shows this behaviour.

Next up, the hard disc, hard drive, disk drive, take your pick.

Back to Basics - The CPU

The CPU, or central processing unit, is the heart of the computer. If your computer has a little Intel Inside sticker on the system case then the CPU is the bit made by Intel, though not all CPUs are made by Intel. It is the CPU that executes or runs programs (such as a word processor or a web browser) through the means of digital logic circuits within the CPU chip.

The CPU consists of a single microchip mounted on a supporting structure of connector pins. It is these pins that mate up with the CPU socket on the motherboard and through these pins that the CPU can communicate with the other electronic components either integrated into the motherboard or connected to the motherboard. The pictures on the left show an actual Intel Pentium 4 CPU. The picture furthest left is of the underside of the chip and shows the array of pins around the processor that will plug into the motherboard CPU socket. The picture near left shows the top of the CPU as it would appear when inserted in the motherboard.

In addition to Intel, there is really only one other player when it comes to CPUs for PCs and that is AMD. AMD has been the arch rival of Intel for many years and has steadily increased its market share. AMD CPUs are generally cheaper than Intel equivalents and this has led to their acceptance by value-based manufacturers such as Dell and Packard Bell.

Irrespective of whether your PC has Intel or AMD inside (and both are equivalent in terms of what they can do and reliability) what determines how fast the CPU runs is the clock speed. Every computer contains an internal clock that regulates the rate at which instructions are executed and synchronizes all the various computer components. The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction. The faster the clock, the more instructions the CPU can execute per second. Clock speeds are expressed in megahertz (MHz) or more commonly gigahertz (GHz). If you have purchased your PC in the last two years it will probably have CPU that runs at a clock speed of between 2.0 and 3.4 GHz. If your PC is 6-7 years old then its CPU may be running at 400-800 MHz. The higher the clock speed of your CPU the faster your PC is capable of running (though other factors can affect the actual performance of your PC).

It's difficult to talk about CPUs and not talk about heatsinks as the two are practically inseparable. Modern CPUs generate a lot of heat, particularly as the clock speeds have increased. In fact they now generate so much heat during normal operation that they would burn out in a few seconds if that heat was not efficiently removed. And that is the role of the heatsink. If you open up any modern PC and look for the CPU you will not be able to see it - the reason for this is that a heatsink is firmly bolted to the top of the CPU chip to draw away the heat it generates. Heat sinks come in many different shapes and sizes, but they all work on the same principle. A heatsink consists of a large piece of heat conducting metal (normally aluminium or copper, both of which are efficient conductors of heat). The piece of metal will have one side milled to a mirror-smooth surface and this is placed in contact with the top of the CPU. Between the two there will normally be a thin layer of a heat conducting paste. The top of our block of metal will normally be shaped to present a large surface area which dissipates the heat to the air and a fan is generally fitted to assist with the dissipation of heat. Here are some pictures of heatsinks.







The CPU is generally the singularly most expensive component in the PC, even though it is arguably the smallest physical component, and can represent over 50% of the cost of your computer. A replacement 3.2 GHz Pentium 4 CPU is currently listed at €420. Failure of CPUs is uncommon, but can happen, often as a result of overheating due to impaired ventilation.

Tomorrow we'll talk about RAM (memory, not male sheep).

Back to Basics - The Motherboard

Now the fun really begins as we start looking at the bits of the PC that you normally never see, and we'll begin with the system motherboard. The motherboard, also called the mainboard, is the large printed circuit board which is the elecronic hub of your PC. Not only does this circuit board host the Central Processing Unit, or CPU, which is the brains of the computer, it also either hosts additional plug in process cards or has features that can come on plug-in cards actually built into the motherboard itself. More on this in a minute.

Let's start by having a look at a typical motherboard. This one is for an Intel Pentium 4 CPU and the CPU chip will plug into the Socket 478 Connector at the top center of the board (more on CPU chips again). Next we would have the memory chips or RAM (random access memory)plugged into the vertical blue and black slots in the upper right section of the board (labelled DDR DIMM Memory Slots - DDR DIMM stands for double data rate dual in-line memory modules, we love our acronyms in the PC business!).

Many of the features we find on a modern PC, such as an Ethernet port to connect to a local area network, a modem to dial into a network, sound capability to allow music and sounds to be heard, graphics capability to permit us to see our system on a monitor, used to require separate expansion cards which were plugged into expansion slots on the motherboard. So, if you wanted to dial into the Internet you would have had to physically install a modem in one of the five white horizontal PC slots you can see in the bottom left of the board. With the advances in motherboard design in recent years you can now find motherboards with all the extras built in, leaving the PC slots more or less redundant for many users. A function that used to require a separate expansion card in the past has been minaturized to just one more chip integrated into the motherboard. However, not all functions have yet been integrated into the motherboard so, for example, if you want a PC that can display TV on your monitor, you will need to add a TV tuner card to one of your PCI slots, like one of the ones in the picture. Also, some of the funtionality integrated into motherboards is often quite basic, a good example being the graphics processing capability built into many motherboards. The onboard graphics chip will display your screen perfectly adequately for 2-D applications, such as your word processor or web browser. However, these are generally completely inadequate for playing 3-D games of the type that are common today. While some of these games may run, they will run very slowly or jerkily and the experience will be frustratingly poor. Because of this a whole market has arisen in add-in graphics cards and these are plugged into the brown horizontal slot, above the PCI slots, labelled AGP 8X Slot (AGP = accelerated graphics port).

The optical drives (CD or DVD) in the front of your PC are connected to the blue and black IDE connectors on the right side of the board by flat ribbon cables, normally grey in colour. The floppy disc drive, if you have one, is connected by a similar cable to the FDD Connector, again on the right side of this board.

Power is brought to the board by means of two connectors that extend from the power supply unit (PSU). These are plugged into the ATX Power Connector (beside the FDD Connector) and the 12V ATX Power Connector at the top left of the board.

The Back Panel Connector (top left edge of board) contains the only part of the motherboard that you are likely to see from time to time. This is the collection of sockets that you connect your mouse, keyboard, monitor, printer, and various USB devices to and this protrudes through a slot at the rear of your system case, like in the picture. You should note that while the motherboard in your PC will have all of the elements that I have highlighted they may be in a completely different location than in the example above. There are thousands of different motherboard designs and each manufacturer will lay out the components on the board differently.

Back to Basics - The System Case

The system case, at its most basic, is a box made of steel or aluminium, the former often covered with plastic, that houses all the electronics that comprise your computer. It will have a power on switch and may also have a reset switch. Probably it will have a couple of lights on the front panel, one indicating the power on status and the other displaying hard disk activity. Normally there will be a vent at the front for air to pass into the case and another vent at the rear for air to pass out. At the front there will be positions for mounting optical drives (CDs/DVDs), floppy drives (getting less common) and card readers (getting more common).

There are a number of distinct physical formats that cases come in, but the most commonly encountered format in the home is the midi-tower which stands vertically. Though less common, you may have a desktop case which sits horizontally on the desk. Also starting to appear in the market are small format cases such as the Shuttle series.








The purpose of the case is threefold. First it provides a structural framework in which all other components can be mounted. Secondly it provides protection to the sensitive components that make up your PC from electrostatic discharge and from physical damage (imagine the damage your cat might do if he got access to the computers innards!). Finally it provides correct ventilation for the removal of the often considerable heat that modern PCs generate. Without this heat removal the PC would overheat and fail.

To get inside a typical midi-tower case normally involves removing a couple of screws at the rear of the case that hold the side panel in place. Once these are removed the side panel generally just slides off.
The picture at left shows an empty midi-tower case with the side panel removed and before any of the electronic components have been fitted. While a lot of midi-tower system cases may look different on the outside, they all conform to a standard, known as the ATX standard, on the inside. This standard ensures that all power supplies that conform to the ATX standard will fit the case, and that the mounting points for the system motherboard are all in specified positions. There is a standard location in the system case for most of the electronic components that make up your PC. With reference to the picture on the left, the power supply unit will be located in the top left corner of the case, the optical drives in the top right, the hard drive(s) in the bottom right and the system motherboard (more on this later) in the main open area.

The rear of the system case is where the sockets on the motherboard emerge, as well as the sockets on any PCI expansion cards or AGP/PCI Express video cards that may be fitted - we'll be covering more on those in future Back to Basics episodes. For now I'll leave you with a picture of the rear of a typical midi-tower system case that has yet to have any internal components fitted.

Next up, the innards.

Back to Basics - Mice and Keyboards

While the monitor allows you to see what your input to the computer is and what the computer's response, or output, is to that input, it is the mouse and keyboard that allow you to get your inputs into the computer in the first place.

There are three basic ways in which the mouse and keyboard can connect with your computer. The first and oldest way is via PS/2 connectors which were introduced by IBM in their first personal computers and were widely adopted by other manufacturers. These are 3/8" round 6-pin connectors that plug into corresponding sockets at the rear of the system case. Over the years a semi-informal colour coding of the connector and socket has been introduced with the mouse being colored green and the keyboard coloured violet (note that this is not universally adopted by all manufacturers and orange can be found used commonly for the keyboard). The connectors and sockets are keyed, which means that the connector will only go into the socket in one particular orientation. Trying to force the connector into the socket in the wrong orientation can lead to damaged pins, a not uncommon problem. While all older PCs and most newer ones will have PS/2 sockets fitted, some newer PCs designated as "legacy-free" do not have them. This is rarely a problem as most newer PCs can use mice and keyboards based on USB connectors. One point to note is that although PS/2 connectors for the keyboard and mouse are physically the same, if you plug them into the wrong socket at the back of your computer the machine will generally stop booting and present a "keyboard error" on the screen.

The second way of connecting mice and keyboards to PCs is using USB connectors and sockets, which are present on all PCs manufactured in the last 10 years. These will be familiar to most PC users and as soon as you plug in either a keyboard or mouse it should be recognized by Windows as a "HID-compliant device" - HID standing for Human Interface Device, a grandiose way of describing a keyboard or mouse.

The final way of connecting your mouse and keyboard to your PC is wirelessly. Well, it's not truly wirelessly, as you must plug in a small wireless receiver to your PS/2 or USB port (both PS/2 and USB versions are available) and place this receiver on the desk that you are working on. Once this is done you need to pair the mouse and keyboard with the transmitter, normally by pressing synchronisation buttons on both units at the same time. As the mouse and keyboard are not connected directly to the computer they need a power supply to run their small wireless transmitters and this is supplied by batteries, either disposable or rechargeable. I favour rechargeable ones as you don't have the environmental issues associated with disposing of spent alkaline batteries.

Keyboards can now be purchased with all sorts of extra "multimedia" buttons on them that do everything from launching Google to adjusting the volume of your loudspeakers. Personally, I'm not a big fan of these, but if you find the additional features useful and you're willing to pay for them, then go for it.

When it comes to mice there are a multitude of different flavours of the same principle, all of which basically do the same job of moving the cursor around your screen. However, there is only one solid piece of advice that I would give you in relation mice. And it is this. If you still use a mouse with a ball in its base, place it in your bin, put your bin out for collection and buy an optical mouse. Optical mice have no moving parts and consequently do not jam up with fluff and detritus from your desk, resulting in jerky, stop-start movement. Get an optical mouse for around €10 and you'll never look back.

Coming next, the system case.

Back to Basics - Monitors

A number of customers have recently referred to their system case as their hard drive or their monitor as their computer or their hard drive as their RAM, so I thought it might be a good idea to have a quick run through of the various different components that make up your average computer so that we can all have a clear understanding of what's what.

The PC that you have at home will generally have a minimum of four components - these are the monitor, the keyboard, the mouse and the system case. Today we're going to briefly visit monitors and we'll cover the other components in the coming days.

The monitor is the part of the computer that you spend most of your time interacting with so make sure that the one you have is easy on your eyes and correctly set up. Up to 2 years ago the commonest type of monitor was cathode ray tube (CRT)-based - using similar technology to standard TV sets. These monitors can give very good pictures but suffer from being bulky, especially those with a screen size over 17", and they consume quite a bit of power. CRTs are being phased out and now it is almost impossible to buy one, except very expensive high-end units used for critical colour work. They have been replaced by LCD flat screen monitors that take up much less desk space and use a lot less power. Typically these are 17" or 19" diagonally across from top-left to bottom-right and prices have fallen dramatically over the past 12 months - you can now but a 17" model for just over €200.

As well as a power cable your monitor will have a cable with one of two types of connector at the end. CRT monitors and cheaper LCD will have a 15-pin D-Sub connector (although there will probably only be 14 pins present) and this is connected to a corresponding female socket, which is almost always coloured blue) on the back of your system case. More expensive LCD monitors will have a cable with a beige DVI (digital video interface) connector that mates with a beige female connector on the back of your system case. The DVI connector keeps the picture in the digital realm as it passes from the computers graphics processor to the monitor. On the otherhand, the D-Sub connector handles a signal that has been converted from digital to analog. In theory the DVI cable (and the graphics processor that it is connected to) should give a better picture, however, we have both digital and analog monitors here at PC Medic as well as one dual input monitor, and we can't honestly say that there is a big difference in picture quality, at least for what we use our monitors for.

What we commonly see in home PCs are monitors that are poorly set up, particularly CRTs. There are three important things to consider with CRT monitors - the screen refresh rate, the picture geometry and the screen resolution. Screen refresh rate is how many times a second the image is redrawn on a CRT. If this is too low, say 60 Hz, you may find that the screen appears to flicker and this will lead to eye strain after some time. Your screen should be set to the highest refresh rate supported by your monitor, in line with the manufacturer's guidelines (see handbook that came with monitor). Screen geometry is how the picture is aligned on the screen and this can normally be changed by using a combination of buttons on the front of the monitor together with an on-screen display (OSD.). Using the OSD you should be able to adjust the horizontal and vertical size of the display (commonly badly set up by users leading to an under utilized screen with a dark edge around one or more sides of the screen) as well as picture position and correct for barrel and pin-cushion distortion. Screen resolution dictates how many pixels, or dots that compose the image, are present on the screen. A low resolution, say 600x800, on a 19" monitor will mean a very chunky display that requires much scrolling to see the full image. Conversely, a resolution of 1200x1600 on a 15" screen (if supported) will lead to a highly detailed screen but with the characters and icons too small to be easily readable. My own preference is for resolutions of 1024x768 for a 15" screen, and 1200x1600 for a 17"-19" screen.

Refresh rate and geometry settings are not relevant for LCDs but screen resolution is, so find the optimum level for your screen.

Next up, of mice and keyboards.