Using Personal Computers

Section 1: An Introduction to Computers

Part 1: The Hardware

	The aim of this first section of the course is to give a general introduction to computers so that you understand the terms and concepts used in the rest of the course. We will look at: The basic parts of a computer and what they are for What the operating system (Windows) is and why we need it How information is stored and organised on a computer

	Think of hardware as the parts of the computer you can touch. The software is the information and programs that are stored inside the computer.
	A microprocessor is a type of silicon chip. However, not all silicon chips are microprocessors. Other components in a computer, such as the memory, are also types of silicon chip. The technical name for a chip (if you want to impress people!) is an "IC", which is short for Integrated Circuit. Most of the microprocessors used in PCs are made by Intel, but there are other makes such as AMD and Cyrix. The "Intel Inside" label on a PC does not necessarily mean it is a better PC.
	Do not get the memory confused with the hard disk. Adding more memory will not allow your computer to store more information. It does, however, allow the computer to process more information more effectively. Adding more RAM is often the easiest and most effective way of making a computer faster and more responsive.
	The CMOS RAM is powered by a battery inside the computer so that unlike other RAM it does not lose it's contents when the power is turned off. If this battery goes flat (rare - the battery often lasts the lifetime of the computer), or something else corrupts the contents of the CMOS RAM, then the computer may not "boot up" (start up) correctly, or may have problems such as not being able to access disk drives. To cure this it is then necessary to run the "BIOS Setup" program (which we will touch on later in the course) to correct this. It is best to leave the BIOS Setup alone unless you understand it well, as mistakes made with this can stop your computer working.
	This clock is powered by the same battery as the CMOS RAM. If the date and time in the computer is wrong (for example, because the battery is flat), then the computer can fail to operate correctly. It is important to have the correct date and time set in your computer even if you don't have programs which use them. The "millennium bug" should not be a major problem for most home computer owners, but it may cause minor inconveniences after the year 2000. Some PCs will not work correctly after 2000, but some of these can be corrected by making an adjustment to the BIOS Setup after that date. Programs are available to check a PC for the millennium bug. Alternatively, it can be checked manually using the BIOS Setup by someone who understands it.
	The hard disk is where everything is stored in your computer. The programs and applications, and Windows itself, are all stored here, along with any files that you save to the hard disk. The hard disk is normally called drive "C:". If your disk is "partitioned" (see later on in these notes), then drive "D:", "E:" etc. may also be on the hard disk. It is possible (but not very common) to have more than one hard disk. If you run out of space on your disk, it is possible to either add another, or replace the one you have with a larger one. Hard disks can fail, losing valuable data. It is a good idea to back up your disk periodically. Backup is discussed later on in the course.
	Sometimes (for reasons only significant to computer programmers and electronic engineers) a kilobyte is defined as 1024 bytes instead of 1000 bytes. Likewise, a megabyte can be 1,048,576 bytes (1024 1024) instead of 1,000,000.
	Floppy disks are a lot slower than hard disks, and do not hold much information. Some people still save all their work onto floppy disks, but it is much better to save to the hard disk. Important files can then be periodically backed up to floppy disks for extra safety if desired. Floppy disks should not be placed near magnets. This includes loudspeakers and TVs. Floppy disks are so called because inside the hard plastic case is a soft, flexible disk. This should never be touched, as the information on it may be damaged. Floppy disks are being replaced in some applications by newer devices (see the next couple of slides) but are still widely used at present. It is possible for your computer to catch a virus from an infected floppy disk. Beware of disks given to you by other people.
	CD-ROMs have largely replaced floppy disks for distributing software. They hold much more information and are much faster than floppy disks. Newer CD-ROM drives are also much faster than the early ones. It is possible to get CD-RW disks which (unlike CD-ROMs) can be modified. A CD writer is required to store information on these disks, and these are not normally fitted to PCs as standard. However, they can normally be read by the standards CD-ROM drives fitted to most computers.
	Tape drives are only really suitable for backing up large quantities of data. The tapes are relatively cheap, but are slow and not particularly easy to use. There are various types of removable disk available, holding anything from a few megabytes to several gigabytes. The ZIP drive, which holds 100Mb, is currently the most popular. The SuperDisk is also becoming popular, because a SuperDisk drive can also read and write ordinary 3.5" floppy disks. External drives which can be moved from one computer to another are available for some of these disks. This makes them useful for moving large amounts of information from one computer to another, even if the other person does not own the same type of drive. DVD disks are the next generation of CDs. They are expected to eventually replace CDs and video tape, as well as CD-ROMs, but this is still new technology at present.

	Keyboard connector. There are two sizes of keyboard connector available. The smaller one is the same size as the PS/2 mouse connector (see below). If buying a new keyboard, make sure that you get the right size. Mouse connector. Not all PCs have a PS/2 mouse port. Two types of mouse are available: PS/2 and serial. A serial mouse plugs into a COM port (see below). If your PC has a PS/2 connector, use a PS/2 mouse. Otherwise, use a serial mouse. Some mice come with adapters and will fit both types of port. Serial ports. These are also known as COM ports or RS232 ports. They are mostly used for mice (see above) and external modems. Most PCs have two of them. There are two types of connector - 9 pin and 25 pin. Adapters can be used to convert from one to the other. Parallel ports. These are mainly used for printers, but can be used for other devices such as some scanners and external disk drives. However, the parallel ports on some older PCs may not be suitable for these purposes. Monitor output. Almost all modern PCs use the same type of monitor connector - a VGA connector. Sound ports. Most newer PCs have sound cards. The connections on these can vary - there may be separate speaker and line out connectors - so be careful when connecting to them. Many also have a combined MIDI/games port.
	Adding extra cards to a PC can cause conflicts with existing cards, especially with older PCs. Newer PCs with "Plug and Play" capability make the task easier (as long as the cards fitted are Plug and Play compatible), but this can still cause problems. System expansion will be looked at later on in the course.

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