Computer Systems

Basic Components Auxiliary Storage OutputProcessor Main Memory Input

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

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

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 to output devices

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

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.

Auxiliary Storage  Hard disk –Stores operating system, systems and application software, and data. –Typical sizes are now Gb  Floppy disks –Typical HD disk has capacity of 1.44 Mb.  CDs –Typical capacity of Mb.  Zip Disks –Capacity 100 and 250Mb disks. Internal or External models available.