The difference between a laptop and a netbook/netpad is a matter of size and facilities. A modern laptop is a fully fledged computer in a compact form, with the speed, memory size, and drive capacity that you would expect from a desktop machine. It can be operated from mains power or from a built-in battery (for a few hours). The netbook is intended as an accessory to a desktop or laptop, often with a faster boot-up time, but with limited memory, smaller screen, battery life, and hard drive size; quite often the hard drive may be replaced by a solid-state drive (SSD) so that the computer is much quieter than a laptop. Netbook machines also usually dispense with an optical drive, so that new software has to be loaded from the Internet or from a flash drive (pen drive).

The netbook market has for some time been served by processors from Intel (Intel Atom) and from AMD (AMD Neo, though a new processor is rumored at the time of writing). Both of these are low power (in the wattage sense, so as to prolong battery life) but run at quite high clock rates, typically 1.6 GHz. Both are being used in netbook applications, though AMD have insisted that the Neo is not aimed at this market, despite a version of the ASUS Eee appearing with this processor. New processors for this important market can be expected to appear over the next few years.

The ARM type of machine, typified by the first netbooks selling for under £100, uses a processor that can be identified as ARM or VIA. The ARM chip is a 32-bit processor that has been developed from the processor used for the Acorn, a machine much loved in its time. The chip is of the type known as RISC, meaning reduced instruction-set computer to reflect the point that it used a small number of simple instructions as distinct from a large set of complex instructions as found in the Intel and AMD processors.

Most of the mobile phone manufacturers worldwide use a form of ARM chip, and they are also used in calculators, game consoles, hard drives, and routers, to name just a few of the applications for this versatile chip which can be customized for any specific application. The ARM processor technology has also been licensed to other manufacturers who use different names. Later versions of the ARM processor are now the processor of choice for the new tablet computers.

Taking a typical netbook/netpad use of ARM, the processor works at the low clock speed (by modern standards) of around 400 MHz, and though the processing speed is adequate for requirements such as document writing and display, photo display, video display, Internet browsing, and spreadsheet use, it cannot cope with such activities as video editing and any use of downloaded software (such as applications like YouTube or Facebook). It is suitable for anyone who has a desktop or fully featured laptop as the main computer and who will use the netbook as a way of working on office documents away from home. The OS is usually Windows CE-6, of which more later. Memory can be added by way of a camera-style secure digital (SD) card, and the USB sockets permit the use of attachments such as memory sticks, optical drive or hard drive and other USB connected items (but not a USB WiFi). For anyone who has been accustomed to using Windows (XP onwards) the CE version can appear very strange and clumsy.

Only the PC type of desktop machine offers the chance to build or repair your own computer easily, because all of the parts that are needed can be bought on the open market. The main parts are the case, the motherboard, and the processor, and you will find case/motherboard packages on offer. It is a fine piece of judgment, because you need to buy items that are compatible and which will not become out of date too quickly, yet sufficiently established to be sure that any problems have been sorted out.

If you go down the road of buying a combined case/motherboard package you will not have to cope with the most difficult choices and construction actions involved in fitting a motherboard to a case. You need only install the processor and, again, choice is important because the processor must be compatible with the motherboard, and the number of pins on a processor increases for each new generation of processors.

The remaining items are memory and disk drives, because the motherboard will incorporate such items as USB and other ports, and probably sound card and video graphics card as well. Memory is too important to buy from unnamed sources because it must be exactly matched to the rest of the hardware, and the memory selection sites for Crucial and Kingston can be recommended with confidence. The optical drive (usually a DVD rewriter) and hard drive(s) can be bought from any supplier as long as you keep with well-known makes.

If you are interested in constructing a PC to your own specification, see the Newnes book Build and Upgrade Your Own PC, currently in its fourth edition.

The original PC machine of the early 1980s was supplied with an OS called Microsoft MS-DOS (DOS meaning disk operating system). This was (and still is, because it still exists as part of Windows) a command-line instruction ( CLI) system. To carry out an action, a command was typed, together with any required data, and the C/R key was pressed to implement the action. This OS followed the pattern established for larger (mainframe and minicomputer) machines, many of which used manufacturers’ own OS.

From 1969 onwards, however, an OS called Unix had become the first choice for many types of large computers, though at the time it was much too large to use in microcomputers. Unix became the OS of choice when it permitted use by several terminals ( multiuser) and the ability to run more than one application at a time ( multitasking). The importance of Unix is that it has heavily influenced some types of OS for modern machines (see later).

The CLI is still regarded highly by computer professionals for its speed and the range of control that it permits over the machine. Research at Stanford University, later extended by Xerox Laboratories, developed an alternative, a scheme using windows, icons, and a mouse, that we are so familiar with today. This was implemented by Xerox in 1981, and was adopted for an Apple machine (Lisa) in 1983 and by machines from Commodore and Atari later. This type of OS is known now as a graphics user interface ( GUI), rather than the Windows icon mouse processing (WIMP) title that was preferred by those who thought that any departure from CLI was a retrograde step. All OSs for small computers now permit use either as CLI or as GUI.

When you buy a new computer you usually have little or no say about the OS. A PC will normally come with the most recent version of Microsoft Windows and a Mac with the most recent version of Mac OS. A few assemblers of computers will install the OS you want for a PC, which gives you the choice of Windows or Linux. If you are assembling your own computer or updating an old one you also have this choice, and it is worth pointing out that older machines that have difficulty running a modern version of Windows will often run very well on Linux (which comes in either 32-bit or 64-bit versions; use the 64-bit version only if you have a 64-bit processor). A further advantage is that several versions of Linux are distributed free, including a full suite of useful software.

Windows has been the standard installed OS for PC machines since the first really usable version, Windows 95. Subsequent updates have been named in the sequence Windows 98, Windows NT, Windows 2000, Windows Me, Windows XP, Windows Vista and Windows 7. Windows 8 is expected in 2012. Of these, the sequence from Windows 95 to Windows XP has featured ever-increasing complexity and more demands on resources of memory size and processor speed, though Windows 7 comes in six versions of which the Starter is the least demanding but likely to be found only on notepad/netbook machines. The next up, Home Basic, is not available in the UK at the time of writing, and the appropriate version for home users in UK and Europe is Home Premium. Other versions are aimed at the professional user and are priced accordingly. If you are currently constructing or updating a PC, then a genuine XP Home Edition installation disk is probably the best option for price and capability.

What follows is a brief guide to installation. Note that OS versions now come on compact disc (CD) or digital versatile disc (DVD) because floppy drives are no longer fitted to computers. The snag with putting Windows XP on to a machine that you are building is that this version of Windows (like subsequent versions) will not work for more than 30 days until it has been activated by Microsoft. This is an antipiracy move, and the activation can be carried out over the Internet (automatically) or by telephone. Windows XP is set up to detect changes in your hardware, so that it will resist being copied to another computer, but a side-effect of this is that changes to your hard drive, memory, or other internal hardware may trigger a request for reactivation. This is not such a problem as you may think, and some users have reported that reactivation has not been needed even for a hard drive change. The reactivation procedure following a change of hardware (as distinct from a change of computer) seems to be reasonably flexible.

The installation of Windows XP Home Edition is started by inserting the disc into your CD-ROM drive, and you may have to set the CMOS RAM (see later) to boot from the CD-ROM. You will be asked to choose one of three options, to install XP completely, to perform other tasks, or to check that your system is compatible. This last option is useful if you are installing into an old machine that has been upgraded; there should be no compatibility problems if you are using a fairly new machine (2005 or later) with components of known quality. If you run the compatibility check you may end up with a list of hardware that needs additional files to be installed. This list may not correspond to reality, because if old hardware has been removed it leaves files on the hard drive that the compatibility list senses as indicating the hardware being present. The additional tasks list contains the following options: If you have files and settings on an old computer, you should use the ‘Transfer files and settings’ option to ensure that you have all the data and items such as e-mail and browser settings. You should also read over the release notes in case there is a reference to some problem that may arise.

All OS types have an initial display that guides you to other software, making it easy to find the applications that you want to use. Figure 15.1 shows this panel for Windows XP, obtained by clicking on the Start button that shows when you switch on.

Once this has been attended to you can select the ‘Back’ option and Install XP. This is a completely automated process and by the time it finishes you will be running your new OS. The format of installing XP was carried over into Vista (not a universally liked OS) and Windows 7 with few significant changes.

Windows CE (or WinCE) is a cut-down and modified form of Windows intended for netbook computers, particularly for embedded OS (in ROM so that it cannot be altered by a virus). Though the software looks familiar, the usage is not always straightforward, and tasks that seem everyday on desktop Windows, such as dragging a file from one part of memory to another, are complex or, in some cases, nearly impossible. WinCE can be implemented on any computer using a processor of the Intel x86 family, and also (in a different version) on ARM machines (making it the OS of choice for netbook machines).

WinCE is intended to run in a very small memory (by modern standards, remembering that my first computer used a whole 32 kB of RAM) of less than 1 MB. The netbook type of computer can operate with no form of disk drive, with the OS and all the available user RAM in solid-state memory. Such machines rely on devices such as SD memory cards and USB memory if more memory is required.

The current version of Mac OS, at the time of writing, is OS X 10.6.6, and you can buy this version if you own an older machine. You cannot, in theory, install OS X on a PC, but as you might expect, someone has come up with a method. If you take this path, you can expect any problems you encounter to be ignored by both PC and Mac advisers. You can also run Windows on a Mac, but until very recently this was equally hazardous. You can run Linux on either type of hardware, but that is something we will look at later.

The old generation of Apple Mac was bought mainly for graphics applications, whereas the PC was traditionally bought for text-related work. The distinctions have become blurred over the years, and though the PC running Windows is by far the dominant machine, some firms have been replacing PCs by Macs on the grounds of better defenses against viruses (a factor common to all OSs based on Unix).

The Mac OS X is frequently updated by Internet downloads, more often than Windows and probably about as frequently as Linux. The current version is referred to as Snow Leopard, and this reference to animal names seems to be popular with non-Windows OSs.

Mac OS X can be used as a command line system, with commands that will be familiar to anyone who has used Unix or Linux. Most users, however, will make use of the GUI called Aqua.

Linux started as a freeware version of Unix. From the start of microcomputing there has been a movement that believes that software should be free and widely distributed. In 1983, the GNU project was launched to develop Unix-based software that would be free to users. Linus Torvalds at the University of Helsinki then developed his own version of Unix, using GNU applications.

The Linux OS is unique in the sense that it can be obtained free in source-code form (the instructions in text that can be converted into microprocessor instructions), so that any user with advanced programming skills can modify and distribute a version. This is why so many versions of Linux are available. Not all versions of Linux are free, but most of the applications that run under Linux can be downloaded free from the Internet. The applications may be developed by a small group of programmers or by a large corporation (for example, the Open Office suite was developed by Sun Corporation, and subsequently sold to Oracle Corporation). The fact that so many applications are also available in source-code form means that improvements can be made continually by programmers other than the original developers.

A useful feature of Linux is that versions of it can be installed on a very wide range of hardware, from mobile phones and netbooks to desktops and laptops, and also to mainframe and supercomputers. Web servers in particular are likely to use Linux, and the uptake on PC desktop machines is on the increase thanks in particular to the free versions from Ubuntu.

Linux can be bought on CD, or downloaded to your existing PC and then burned on to a CD or a flash drive for installation. The packaging comprising Linux along with a selections of applications constitutes a Linux distribution ( Distro), so that by installing a distribution you have a good OS and practically all of the applications that you are likely to need. The cost saving is quite spectacular if you compare this with other OSs and applications. Well-known distributions include Ubuntu (a particularly good choice if you are switching from Windows), OpenSuse, Fedora, and Red Hat.

The Ubuntu distribution is, at the time of printing, in version 11.04. The numbering system consists of year, decimal point, and then month digits, so that new versions appear in April and October each year. If you are installing for the first time you can download an installation copy that you burn on to CD and then install. From then on, updates come through the Internet with no need to use a CD.

The desktop version is usually supported for three years and the server version for five years, but you may find that the version that you use needs very little support after three years and unless problems arise you can use it indefinitely. One point to remember is that when you install from CD, this usually scrubs the memory, so that if you had an old version and wanted to install a new version from CD, you need to keep your files and settings by saving the disk folder called ‘Home’. An Internet upgrade has no effect on the Home folder contents.

Figure 15.2 shows part of the typical starting screen view for Ubuntu Linux with the other menu portions of Places (folders and drives) and System (change essential features).

One very useful point about the Ubuntu distribution is that the CD allows you to run the OS (slowly!) directly from the CD, so that you can try it out without committing yourself to it until you are happy to use it. This is also a feature that allows you to recover from a disaster that has left your computer locked up. The form of the GUI looks familiar, so that if you have used Windows or Mac OS X you will quickly settle to Ubuntu. The amount of support is impressive: the community of users is always available to discuss problems or misunderstandings, and if you make it clear that you are new to the system you will not be responded to with incomprehensible programmer-speak. All this has made Ubuntu an excellent choice for anyone who has built or upgraded a computer for himself or herself.

One class of software that causes more problems than any other is the driver. A driver is a piece of software (which can be quite large) that enables your computer to use a piece of hardware. For example, a printer will need to have a driver in your PC, and if you change to a different make or model of printer you may have to change the driver as well. It might be possible to use the printer for some text documents without a driver, but for anything else you definitely need to have the correct driver installed.

The same is true for your monitor, scanner, WiFi adapter, and any other hardware apart from keyboard, optical drive, and mouse (and even some mice need a driver if they include features that are not part of a bog-standard mouse). A graphics board will almost certainly need a driver if you are to use it for anything other than displaying text.

For the Windows user, drivers should not be too much of a problem because all hardware that needs a driver will include a Windows driver on a CD. You need to be sure that the driver is the correct one for your version of Windows, but unless you are using something prior to Windows Me you are unlikely to have any problems. It is more of a problem if you acquire a piece of hardware that has lost its installation CD.

Though you can download drivers from the Internet, you have to be really careful about specifying the hardware correctly. If you glance at the driver list for HP printers, for example, you will see what I mean. An added complication is that some hardware has drivers from Microsoft already in your PC but the manufacturer has provided different drivers. The safest way out is to use the Microsoft drivers unless you find that they are really unsuitable (which is unusual).

Life is not quite so easy or inexpensive for Mac users and is much more complicated for some Linux users. New hardware nowadays is likely to provide Mac drivers as well as Windows drivers, though older hardware might not, and you might not be able to find suitable drivers. Drivers for Linux are very often built into your Linux distribution, but you cannot be sure until you check it out. Certainly you should not expect that very new hardware will have a Linux driver when it first goes on sale, but if the hardware is widely used you can be fairly sure that someone in the Linux community will write a driver.

Old hardware can be a pain: I had a very good HP scanner that gave me years of service with successive version of Windows, but no Linux driver was ever available, and I had to solve the problem by looking (on Google) for a new scanner that was Linux compatible (it turned out to be the Canon LIDE, and it has served me really well in my Linux days). If you are building up a computer system for yourself with the intention of using Linux, just check that the hardware you want to use is compatible.

When you install a major application a large number of bits of software are added that you know next to nothing about. An example of this is the codec. The word is derived from code–decode, and it applies to files of sound or video.

For example, if you record a sound from an analog source into a digital file you need to use a codec to convert analog to digital and to compress the digital signals to fit into memory. The compression can be lossless, meaning that when the reverse codec is used to convert digital to analog for a loudspeaker the resulting analog signal will be as near as possible identical to the original. The alternative is lossy compressing, which can greatly reduce the size of a file but with some reduction of quality (which may or may not be easily detected). Another major use of codecs is conversion from one format of file to another.

Codecs are also used for video files where compression is important because of the size of such files. For example, a piece of video using a codec in the AVI format may be of 22 MB for a short clip, using the MPG codec makes this 17 MB, but if the WMV codec is used the size reduces to 1.4 MB (but the quality may not be adequate).

Codecs are widely available, usually free, for a huge range of purposes, and you can convert almost any form of file of audio, still photo, or video into any other if you have the correct codecs. Once again, these are easily obtained for Windows and Mac (though many websites will try to persuade you to part with cash). Linux users working with video have the luxury of a free piece of software called WinFF, and they can also download a large number of other codecs from the Linux sites.

Skype is a system that allows you to make telephone (including videophone) calls to other computer users (and also voice-only calls to any telephone subscriber, with or without a computer). You will need a microphone and (if you want to make video calls, a webcam). You must not use Skype for emergency calls (999 or 911). The software for Skype is free, and uses software that uses the voice over Internet protocol (VOIP) standard.

The service was launched in 2003 and in use it resembles an Internet chat room. Making contacts with other Skype users is free, but if you make calls to a telephone landline or mobile phone you have to pay (though the charges are lower than you would encounter using your own landline or mobile). Payment can be made by buying credits from Skype.