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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
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
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 ….
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
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
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
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
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
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
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– 210 or 1024 bytes = 1 kilobyte (K)– 220 or 1024 x 1024 bytes = 1 megabyte (M)– 230 or 1024 x 1024 x 1024 bytes = 1 gigabyte (G)
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
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’
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
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.
Good Practice - 2
Delete things you don’t need Be TIDY Be ORGANISED Be CAREFUL
Backup regularly