Definition of Computer System: Computer System is an electronic machine that takes data or commands as Input, processes the data according to commands and gives out information as Output.
Devices in the computer system are classified based on their function:
- Input Unit
- Output Unit
- Central Processing Unit
Input Unit consists of devices that are used to feed data or commands into computer
Eg: Keyboard, Mouse, Joystick, scanner etc
Output Unit comprises devices that are used to produce information coming out from computer Eg: Monitor, Printer etc
Central Processing Unit consists of components that are useful in processing and storing. The Units of CPU are 1. Processor 2. Memory
Processor consists of Arithmetic and Logic Unit and Control Unit. The capability of the computer system is estimated based on its processor’s speed. The speed of the processor is measured in terms of Hertz (Instruction cycles per milli seconds)
Eg: Pentium IV, Intel Celeron, AMD Semptron, Core i3 etc
Memory of computer of 2 type:
- Primary/Internal/Main/Volatile Memory
- Secondary/External/Auxiliary/Non-Volatile Memory
Primary Memory consists of Random Access Memory and Read Only Memory.
The Instructions in ROM are used at the time system startup (Booting).
RAM is used by the processor as a temporary work area. The contents of RAM gets cleared off when system is turned off.
External memory devices are used to store information permanently.
Eg: Hard Disk, Floppy, CD/DVD, Pen drives etc.
Memory of Computer system can be measured in terms of Bytes.
1 Byte (8 bits) of memory is used to represent to store a single character.
0 or 1 = 1 bit (Binary Digit)
4 bits = 1 nibble
8 bits = 1 byte
1024 bytes = 1 Kilo byte
1024 KB = 1 Mega byte
1024 MB = 1 Giga byte
1024 GB = 1 Tera byte
