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Computer Systems
Integrated System of hardware and software that enables data to be input, then processed and the
results communicated to the user.
Input
Information converted to data
Validated [check to make sure it's the right type]
Verified [accurate]
Process
Turning data into something else
Central Processing Unit
Output
Communication…

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Microwave links or satellite channels or telephone lines
Peripherals such as printers and software can be shared
Remote location based oil engineers can work
Storing files centrally makes less vulnerable to workstation failure
Communication ­ cheap and fast
Expense of cabling ­ install and replace
Fault with server crashes whole…

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Configurations
Star each connected to central computer [mainframe or server]
Performance unaffected by other workstations
Cable failure less of a problem
Central computer or server failure
Most cabling ­ expensive
Bus/Line line of cable sends data, where terminals are connected
Cheapest ­ least cabling
Slow, as all data on central…

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Menus [list of options]
Pointers [arrow to move screen]



Input

QWERTY keyboard
Key connected to a switch, sending a signal to CPU
Typing skill needed or can be slow

Concept keyboard
Shops/restaurants with options representing data

Mice
Clicking gives a command, held down for dragging
Direction and speed ­ pointing…

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Touch screens

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The CPU
Runs computer programmes, responding to user input
Generalpurpose
Instructions
Program is a list of instructions for CPU, which it performs in order
Load/Store Instructions ­ moving a piece of data move data from memory to CPU and back
Arithmetic Instructions ­ operations and functions
Control Signals ­ temporary…

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Computer Memory
Random Access Memory
Read from to written to
Volatile RAM keeps contents when power is on
Nonvolatile needs power to change contents, but contents are stored
Programs for the computer is on the RAM [easy access]

Read Only Memory
Data and programs for CPU are put onto ROM…

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Using the system
D A T A
Data needs to be gathered first ­ this is data capture i.e. the input
Obtain the information ­ record and convert into a form suitable for use with the computer system
Enter the data into the computer using an input device

Datacapture forms/Questionnaire…

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Fixedlength fields ­ some waste space but computers can manipulate quickly

Variable length ­ less memory, but longer processing time


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P R O C E S S I N G T H E D A T A
Real Time Processing
Processing as soon as entered, within a time window
Quickly respond to changing information
[Air traffic control/Safety devices/Inflight navigation/Quality monitors]
Necessary, but can be expensive as processor is always ontask…

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