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Computer Systems

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Basic Components

Main Memory




Input Processor Output



Auxiliary
Storage

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Types of Input
Keyboard
Mouse
Barcode readers
Scanners
Voice data entry
OMR
OCR

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Types of Output
Monitors (also known as VDUs or screens)
Printers
Plotters
Other types ?

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The Processor
Processing Power determined by:
­ Speed of operation of CPU
­ Amount of memory
­ Number of I/O devices it can handle
Some control functions of CPU:
­ Transmission of input data to memory
­ Process data held in main memory
­ Transmission of data from main memory…

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Main Memory
Made up of individual storage units called bytes
Total number of bytes is referred to as computer's
memory size:
­ 1 Kilobyte (Kb) = 1,000 bytes (actually 1024)
­ 1 Megabyte (Mb) = 1,000,000 (1 million) bytes
­ 1 Gigabyte (Gb) = 1,000,000,000 (1 billion) bytes
­ 1…

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RAM and ROM
RAM ­ Random Access Memory
­ Stores current programs and data.
­ It is VOLATILE ­ lost when switched off
ROM ­ Read-Only Memory
­ NON-VOLATILE
­ Instructions or programs permanently etched onto a
chip. For example, bootstrap loader.

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Auxiliary Storage
Hard disk
­ Stores operating system, systems and application software,
and data.
­ Typical sizes are now 20-40 Gb
Floppy disks
­ Typical HD disk has capacity of 1.44 Mb.
CDs
­ Typical capacity of 650-800 Mb.
Zip Disks
­ Capacity 100 and 250Mb disks. Internal or External…

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