1. Hardware Case that houses the computer Monitor Keyboard and Mouse Disk Drives – floppy disk, hard disk, CD Motherboard Power Supply (PSU) Speakers Ports Additional Slots RAM Memory Cache Memory Bus Fans Printers Modems

2. The Motherboard and CPU Could be considered to be the heart of the computer, consists of: – Central Processing Unit (CPU), microprocessor Coprocessors – RAM, Random Access Memory – Expansion Slots For video cards, I/O cards, Modems, sound cards etc. – Miscellaneous connectors To keyboard, disk drives etc

3. Microprocessors The first microprocessor, Intel 4004, was invented by Ted Hoff in 1969-71 The microprocessor defines the computers speed and power – Speed set by the processor clock (helped by RAM) Evolution of processors – Intel 4004, 8080, 8086, 8088 (limited DOS to 640K of RAM), 286, 386, 486, Pentium….Pentium 4 ….

4. Memory There are 2 main types of memory – RAM – Random Access Memory, volatile memory, constantly used by the computer. Everything in RAM is lost when the computer is turned off. Random because it does not have to be used sequentially – ROM – Read Only Memory, non-volatile memory, stores programmes used to start up the computer. Special equipment is required to programme and erase PROM’s/EPROM’s

5. More about RAM Three categories of RAM – Conventional memory, the first 640kb – Upper memory, 640-1024kb, i.e. the first megabyte – Extended (high) memory, above the first megabyte RAM is where the processor runs all programmes and stores all data. Some applications require a lot of RAM to run. RAM can limit the number of applications you can run or how quickly applications will run Physically RAM can be SIMM or DIMM (Single/Dual-in- line-Memory Module) and it is plugged into the Motherboard

6. Other types of Memory Cache memory – Located close to the processor, (internal or external) faster (about 5 times) and more expensive than normal RAM. Used to buffer normal RAM Virtual memory – Hard disk space that is used to extent RAM. Data is swapped between the hard disk and RAM. E.g. virtual memory can enable computers to run larger programmes than they could otherwise accommodate VRAM – Graphics cards often have their own memory to process large amounts of graphical data

7. ROM ROM holds its data even when the machine is switched off. When a computer is switched on it immediately runs a ‘Boot’ (Bootstrap) program which is stored in ROM. This takes it through several internal tests. ROM is programmed and installed by the manufacturer, it is often referred to as a ‘chip-set’ and cannot be changed or modified while in the computer. But it can be upgraded with a new chip-set

8. Disk Storage – General Facts Disks are covered with a thin magnetisable material on which data (1/0, +/-) can be written and read The Read/Write heads move across the disks as they spin usually at 3600 revolutions per minute The heads never actually touch the disk but use a magnetic beam to read and write data Data is organised on tracks within sectors

9. Storing Data When data is stored on a disk the location of the track and sector is stored in the File Allocation Table (FAT) To retrieve data the processor looks in the FAT table for its location When data is erased it is not actually wiped off the disk but its location is made available to be overwritten

10. Measuring Memory Data is stored in binary digits or bits Each character is defined by 8 bits also called a byte – E.g. 01000001 is interpreted as the character A by the computer Memory is measured by the number of bytes – 2 10 or 1024 bytes = 1 kilobyte (K) – 2 20 or 1024 x 1024 bytes = 1 megabyte (M) – 2 30 or 1024 x 1024 x 1024 bytes = 1 gigabyte (G)

11. Floppy Disks Most are now 3 ½ inch, High Density (HD) with a capacity of 1.44 Mbytes There are also Double Density (DD) disks that have a capacity of 720 Kbytes Disks must be formatted, i.e. divided into tracks and sectors, before they can be used – Most disks now come pre-formatted CD-R or CD-RW – 650 or 700Mbytes of memory. Usually used for multi media applications. Now an option on most PCs, can also purchase CD writers Zip Disks, 100, 250, or 750MBytes

12. Ports Parallel (LPT) use 8 separate channels to send data, don’t work over long distances, fast, configured as LPT1, LPT2 etc. Serial only use one channel, slower than parallel but better over distances USB connectors (Universal Serial Bus) allows ‘hot swapping’

13. Networks Computers can be connected together to share resources (e.g. printers), data or applications. Such a connection is called a Network – LAN, is a Local Area Network, used within a small area, e.g. a building or a department – WAN, is a Wide Area Network, used for larger areas, e.g. between buildings, towns etc – Each computer is called a node, workstation or client – The network is managed by a Server, a powerful machine with plenty of Ram and disk space that holds shared applications and controls the flow of data on the network

14. Good Practice - 1 Back up EVERYTHING – Trust NOTHING! Use intelligent file names – Group similar files together in a directory or sub- directory – Use sensible names for directories & sub-directories Don’t keep 2 different copies with the same name – differentiate with version numbers and dates.

15. Good Practice - 2 Delete things you don’t need Be TIDY Be ORGANISED Be CAREFUL Backup regularly