PC hardware

This page makes you very quickly familiar with the hardware, software and cabling elements and numbering systems/units used in relation to PCs (see Ref 1 when a more comprehensive description is needed).

Refering to the above picture, the Personal Computer (PC) usually means the ‘brain’ packaged in a metal box called the base unit. The ‘brain’ (I know it sounds a bit juvenile, but it is an appropriate name) comprises the following functional elements:

A Main or Motherboard (Ref 17), which is a large Printed Circuit Board (PCB) with fixed components and sockets that accept smaller PCBs and other components, hosting:

The microprocessor or Central Processing Unit (CPU) (Ref 18), which has pride of place with its own heat sink and cooling fan even.

Small PCBs with fast Random Access Memory (RAM) (Ref 19).

Interface boards (PCBs) for Hard Disk (HD) Drives (Ref 16), a Floppy Disk Drive (FDD), Compact Disk (CD) Drives and external peripherals (the connectors on the back of the base unit are integral parts of the interface boards for external peripherals).

The HDD, a high-density magnetic storage device.

The User interacts with the PC via the Human Computer Interface (HCI), which comprises hardware and software elements on the Motherboard and associated wiring in the base unit, together with the following equipment to be accessed physically by the User:

Standard Items:

A qwerty (alpha-numeric) keyboard (Ref 25).
A mouse (Ref 26) or its equivalent, eg trackerball.
A display monitor (Ref 27).
An inkjet (Ref 28) or laser (Ref 29) printer.
A Floppy Disk Drive (FDD), integral with and accessed from the front of the base unit (Ref 20).
A Compact Disk (CD) drive, integral with and accessed from the front of the base unit (Ref 21).
An ON/OFF switch with associated indicators, on the front of the base unit.

Optional Items:

A microphone.
A scanner (Ref 30).
A CD writer or burner (Ref 31).
A Zip drive (Ref 32).
A web camera (Webcam) (Ref 33).
A communications modem (Ref 23 or Ref 24) or router.
Various other items, too numerous to list.


Interfaces to peripherals and other PCs are via electrical connectors, which are concentrated on the rear panel of the base unit. As stated earlier, these connectors are actually integral parts of interface boards (or cards) plugged into the motherboard. Connectors for some peripherals, eg the video connector for the monitor (on the video card), the keyboard, the mouse, the speakers, mike and games joystick (on the sound card) and some older scanners are unique to these peripherals. Besides these, a range of standardised connectors called ports are provided. An Ethernet connector (like a fat telephone connector) is provided if a network interface card is installed on the motherboard; this interfaces Ethernet cables to other PCs in a network and cable modems. A parallel, or LPD(1 or 2) port (Ref 41) may be used to connect to a Zip Drive and/or a printer, or to a Zip Drive and an adaptor in a mains socket for a home network. A serial, or COM(1-4) port (Ref 42) may be used to connect to a dial-up modem or a mouse. The most popular connector/port is now the USB connector, the interface for which does not require special interface cards and which can also provide the necessary 5 Volt power supply to a modest number of peripherals. A PC typically has two USB ports (Ref 43) and many ‘USB’ peripherals can be accommodated using USB hubs (Ref 44). Although in most situations it is not significant (and sales literature doesn’t normally complicate things by telling you), it is however worth noting that the performance of a USB interface is not quite as good as the interface on an Ethernet card (cost about £12) plugged into the Motherboard (to which Ethernet hubs can be connected allowing many connections).


If you are interested in how to build or upgrade a (desktop) PC, Ref 45 describes the procedures involved, together with the pros and cons of upgrading and replacing. It doesn’t however always make it clear how to ensure upgrade components are compatible with your particular configuration, so you will still have to seek further advice, eg will that Pentium processor work optimally on my Pentium motherboard and what type of memory fits on my motherboard? In all cases, you do need to refer to the manuals for both new hardware and your present PC/motherboard. If I find a better site, I’ll let you know.


In the PC / Internet scene, the following numeric multipliers are used when specifying values of units for performance and other quantities:

n or nano. 1n something is one billionth of one unit of something (users probably won’t come across this, unless looking at ‘nano bio-robotics technology’ or simply the time, in such fractions of a second, that computer operations and communications take at the lowest level).

µ or micro. 1µ something is one millionth of one unit of something (again, you’re unlikely to see this relatively larger value). A variation of this, called a micron, is used to specify light or infra-red wavelengths and gas / dust particle sizes (in millionths of a metre).

m or milli. 1m something is one thousandth of one unit of something (not that common as far as users are concerned either).

k or kilo. 1k something is one thousand units of something (or decimal 1,024, which is 210 if working in the binary system of units).

M or Mega. 1M something is one million units of something (or decimal 1,024 x 1,024, which is decimal 1,048,576 or 220 if working in the binary system of units).

G or Giga. 1G something is one thousand million (billion) units of something (or decimal 1,024 x 1,048,576, which is decimal 1,073,741,824 or 230 if working in the binary system of units).

T or Tera. 1T something is one million million (or thousand billion) units of something. It is a trillion, the multiplier that pops up when referring to the number of dollars in the US Treasury’s (and maybe the number of liras in the Italian) annual budget. If working in the binary system of units, it is decimal 1,048,576 x 1,048,576, which is decimal 4,294,967,296 x 256 or 240 (it is only seen when refering to performance and storage capacity in super-computers).

The most common units seen are:

Bit or binary digit. In everyday work, we operate with numbers to the base 10. Computers operate with numbers to the base 2; a decimal digit has 10 possible values; a bit has two possible values (a logic gate on a chip is either closed for a ‘0’ or open for a ‘1’). It’s useful to know this to distinguish ‘N bits/sec’ from ‘N bytes/sec or ‘N baud’.

B or byte. One byte is eight bits (with a value between decimal 0 and 255) and each alpha-numeric character is represented by a unique binary value (eg 11011010, or decimal 218 – an exercise for you to work that out, or see below), so we use bytes to represent meaningful data (see Ref 4 for details on character encoding if this is of particular interest to you).

The most significant ‘1’ is decimal 128, the next ‘1’ is decimal 64, etc.

One use of the byte is to define memory or storage capacity, which can be either permanent (magnetic or optical) or temporary (electrical). A 3.5″ floppy disc can hold about 1.38 MB (1,457,664 bytes) of data (in permanent, magnetic form), a Compact Disk (CD) can hold about 697 MB (731,617,280 bytes) of data (in permanent, ‘optical’ form), a DVD can hold about 4.7 GB and a ZIP disk can hold 100 MB or 250 MB (in permanent magnetic form). Your Random Access Memory (RAM) chips provide temporary storage for your working programs and data (whilst your computer is switched on) and (in the year 2002) you need at least 64 MB of RAM to be ‘Internet Ready’. Your HDD, providing permanent magnetic storage for all your software and files can hold as much as 40 GB and beyond (a bank of these will provide even more storage). Other references to this parameter include web space available to you on servers (say 50MB) and e-mail storage (say 2MB).

A baud is (nominally) a data transmission speed of one byte/sec, a la dial-up and broadband cable modem speeds. I won’t give examples here because I have to confess to not being sure of my ground regarding the difference in modem speeds between ‘kbaud’ and ‘kbytes/sec’ (I believe there is a subtle difference and no doubt someone will tell me eventually; I just can’t find the time to research everything myself).

Hertz or Hz (for Frequency in cycles/second). Your 3GHz Pentium 4 CPU operates at 3 billion cycles/sec, giving some idea how many operations (processing functions) it performs every second (yes, that’s impressive, if you can remember that each of the 5 inch (12.5cm) long vacuum tube valves used 50 years ago represented only one logic gate). See Ref 2 for a fascinating history of the CPU (microprocessor) used in PCs. There are other references to frequency, such as the speed of the ‘highways’ or busses that transmit data between elements on your Motherboard, ie 100Hz, 133Hz or 266Hz (choosing elements to fit on and match the bus speed of the motherboard is therefore analagous to choosing hi-fi speakers to match the output of your hi-fi amplifier). See Ref 3 for details on CPU and memory speeds if this is of particular interest to you.


The Operating System (OS) in a PC is normally a version of MS Windows (more due to Microsoft’s ruthless marketing skills and monopoly policies than technical excellence, when you consider that Apple first introduced the ‘windows’ concept in the mac.). Its purpose is to provide the software environment needed in a PC for all other hardware and software functions to work. A Built In Operating System (BIOS) (Ref 22), which is not to be confused with the main OS, powered by a small battery, contains sufficient details to provide the means whereby the OS is pulled down from its recorded location on a high density permanent (slow, but does not need power to retain its data) Hard Disk Drive (HDD) magnetic store into a volatile (fast, but needing power to retain its data) Random Access Memory (RAM) on boot-up, ie starting up from cold.

In keeping with my policy not to reinvent the wheel on this website, I’m going to give you links to three other sources of useful information concerning OSs for when you feel like reading more details. The first is a general description of how they work (Ref 34). The second is a discussion forum (Ref 6), in which users can share their knowledge, experiences and problems with all versions of MS Windows (and of related hardware issues actually). The last (Ref 7) provides clear, accurate and easy to understand user and configuration knowledge relating to all versions of MS Windows.


Software applications are pulled down from the HDD when required and operated inside the OS environment in the RAM by the User to perform the tasks for which the PC is currently being used:

Word processing, eg MS Word and Corel WordPerfect.
Calculations and spreadsheet generation, eg MS Excel and Lotus 1,2,3.
Database creation and access, eg MS Access and Omnipage.
Graphics design and desktop publication, eg jasc Paint Shop Pro and Adobe Pagemaker.
Website design, eg Macromedia MX suite and MS FrontPage.
Others, too numerous to list here.

The products of these software applications are normally User-created files that can be subsequently stored, changed and used for their intended purposes. However, some applications simply perform functions, so don’t have products as such, eg FTP Clients, which provide a User interface to upload (transfer from your PC) websites to their hosted spaces in servers using a format known as the File Transfer Protocol (FTP) and Internet Security / Virus Scan software, which provides a firewall (Ref 35) and protection against viruss (Ref 36), trojans and identity theft (Ref 37).

Hard-copy user guides and online tutorials for these are often provided by their manufacturers and all of the good ones come with an indexed windows or html-based help system. However, these are often not very user-friendly, eg because they provide far too much low-level detail without first defining the essentials from the top down. Make no mistake though – your most important Application is, of course, your Internet Security (or at least Anti-virus) package. External tutorials and discussion forums that are referenced from this website provide details on this and other types of Application, but it’s worth clarifying a few things about software firewalls before you ‘can’t see the wood for the trees’ (these ‘wrinkly’ sayings are still very relevant, as far as I’m concerned!).

If (instead of a cable modem on a broadband system) you have a router with a hardware firewall, you can configure this firewall to control incoming communications (not outgoing ones), so you will have to coordinate this with your software firewall.

If your OS is Windows XP+, you need to disable the built-in firewall provided by XP (via Control Panel>Network Connections, etc or similar), to allow your imported firewall to work without disappearing up its own starfish.

As in most situations where you’re changing a configuration in your PC, a golden rule in each of the following situations is to keep a detailed handwritten record of what you’ve done, so that you can retrace your steps if necessary.

Then you need to set your security software going on its scan to produce a list of the Internet-enabled programs lodged in your PC (if you’ve already been there and done that, maybe this is just a list of the ones you haven’t already set firewall rules for, eg in Applications you’ve since installed). For each executable program in this list (.exe or .dll, etc) we have one of two options:

One option is to allow it to be set up ‘automatically’ and then (later) when you get an Alert associated with this/these program(s) to decide for yourself if you’re happy to allow it/them to relay details of your system to the outside world, ie set it/them up to ‘block all’, ‘permit all’, ‘automatic’ or ‘custom’, remembering that the minimum you need access for is your Internet browser (eg Internet Explorer) software, e-mail (eg Outlook Express) software, FTP software for your website/P2P/etc uploads, and Internet security/virus checking software (eg Symantec’s Norton Internet Security 2003). There are other files demanding access, some you may need and some you don’t (such as Telnet until you’re into server-side scripts) and a full explanation of these is beyond the scope of this document, so here’s where you ‘permit’ if you don’t know but go into the firewall Program Control dialogue to tweak (see below) as and when you ‘learn the ropes’ (and after any obviously malicious communication attempts). Remember that the bottom line here is you’re configuring the communications allowed (‘TCP’ and/or ‘UDP’, via all or specified local and/or remote ports related to a specific file in your PC to and/or from all or specified external computers). Other alerts may also appear, but these will be related to (incoming only) TCP or UDP communication attempts that don’t relate to any specific program on your PC (see the Advanced>General firewall rules below).

The other option is to go straight into the Program Control dialogue in your security software and set it up yourself from the start (to ‘block all’, ‘permit all’, ‘automatic’ or ‘custom’), remembering that the minimum you need access for is your Internet browser software, e-mail software, FTP software for your website/P2P/etc uploads, and Internet security/virus checking software and you need to decide on other files demanding access (do you really want Media Player to waltz off to Microsoft every time you use it, ostensibly to find a codec, but in reality posting details on what’s in your PC? – better to just have the latest version installed and then select ‘block all’ – if it then can’t play a video, you know that you need to try DivX). Remember that the bottom line here is you’re configuring the communications allowed (‘TCP’ and/or ‘UDP’, via all or specified local and/or remote ports related to a specific file in your PC to and/or from all or specified external computers).

Then you need to set the initial Advanced>General firewall rules, which (unlike the above) are for all external (incoming as well as outgoing) communications that are not related to any specific (either Internet-enabled or otherwise) programs on your PC. Rules at the top of the list in this category override the ones lower down. I set mine to initially permit only essential IPs/URLs (at the top of the list), ie:

Symantec (TCP communications to and from appropriate ports for the URLs of my Internet security Application).

NTL’s homepage and Yahoo! Geocities (TCP communications to and from appropriate ports for the URLs of each of my two free webspace providers).

DNS (TCP/UDP communications to and from remote port 53 for any computer – in the essential DNS system of course).

Loopback (TCP/UDP communications to and from any ports for IP

Then you carry out your daily business, but perform the necessary administration following any Alerts, as described earlier for alerts associated with programs on your PC and as follows for alerts associated with external IPs/URLs, ie from the mob or the many geeks out there in the ether or legitimate (external) sources, eg your security software supplier’s site (to be allowed of course) and basically ‘What do you want to do about it? :

If this Alert appeared in response to an action you have only just taken, one would normally expect it to be safe, but that certainly isn’t necessarily the case so I prefer to block it and persevere with blocking it, then if it gives up trying and there are no adverse effects it’s fairly safe to assume you made the right decision; otherwise it was the wrong one (so you’ll know next time)!

If it suddenly appeared out of the blue, it’s probably unsafe – unless it’s your Internet security software supplier (especially if you’re not currently working via your browser, e-mail or FTP program) isn’t it now? – in which case it seems like common sense to select ‘Block’. Then you need to go back into the Advanced>General dialogue and add a blocking rule for the ‘offending’ local PORT (TCP/UDP to/from all computers) at the bottom of the list unless it’s one of your important ports such as 21 (FTP), 80 (HTTP) or 443 (HTTPS). That action should stop any further such communication attempts and you’ll also soon find out if it causes you any problems with wanted on-line access (in which you will reverse it won’t you). Sorry, it’s a fact of life that you need to be on your toes sometimes when you’re on-line!

At the end of the day, you have (of course) to follow a learning curve in being a detective and do what you think is sensible. One last thing though; when your ISP fails you and you lose all online access (as mine does every now and again), don’t panic and change all your firewall (or modem/network connection) settings (have faith in the settings you’ve spent a lot of time successfully configuring, have patience and bl**dy-well insist that your ISP fixes it – have their Customer Support phone number handy, because you’re not able to complain on-line now!)


A browser, such as MS Internet Explorer (supplied with all MS Windows OSs), Netscape Navigator, Opera, etc allows the User to look at the Internet, by downloading websites, ie transfering them from their hosted spaces in servers to your PC (this will normally be into a cache, ie a reserved storage area on your HDD, allowing second and subsequent viewing of a website to be made without the original data transmission delays) and then translating the HyperText Markup Language (HTML) used on its pages into the appropriate media (video, audio, etc) commands.

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