Basic components of a computer

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Main parts of a PC or workstation:

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CPU

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memory

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busses

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external devices:

user input	keyboard, mouse
screen output	graphic card
permanent storage	hard disks
other	sound card, printer, cdrom, network devices, ...

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CPU: ``Central Processing Unit'', consists of:

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arithmetic and logic unit = ALU (addition, multiplication, comparison etc.)

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registers (extremely fast special memory for commands and operands)

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control unit (gets commands, moves data to/from ALU and memory)

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Type of commands, a CPU understands:

data movement

``get data from memory cell 4228 into register r3''

computation

``add content of registers r1 and r2 and store the sum in r3''

program flow

``get the next command from memory cell 2001, if register r1 contains 0''