A Computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically.
- A computer system is made up of hardware and software components and is capable of:
- data input – using input devices
- data processing – using a microprocessor, typically the Central Processing Unit (CPU)
- data output – using output devices
- It may also be capable of:
- data storage – so data can be stored for later use
- data transmission – so data can be transferred to or from another computer system
The physical components of a computer are called hardware. The set of instructions given to the computer to accomplish a task is referred to as software.
- Input Devices – these include any kind of device which can be used for getting data into the computer system from the outside world. Some examples include; keyboard, mouse, microphone, heat sensors, switches, touch screens, digital cameras and so on.
- Processing Devices – this usually refers to the Central Processing Unit (CPU) which carries out program instructions.
- Storage Devices – these include any device which will store data until it is needed for processing. This can include temporary storage devices, like the computer’s memory, or long-term storage devices like hard-drives, DVD drives or tape drives, etc.
- Communication Devices – these deal with the transfer of data from one computer system to another and include routers which link networks and modems which allow computers to communicate data via the Internet.
- Output Devices – these include any devices which can provide data in a useful format to a user. For example a computer monitor, speakers, printers etc.
The computer memory holds the data and instructions needed to process raw data and produce output.
Computer memory is of two types: Volatile (RAM) and Non-volatile (ROM). The secondary memory (hard disk) is referred as storage not memory.
we can categorize memory into four types:
- Register memory: Register memory is the smallest and fastest memory in a computer. It is located in the CPU in the form of registers. A register temporarily holds frequently used data, instructions and memory address that can be quickly accessed by the CPU.
- Cache memory: It is small in size but faster than the main memory. The CPU can access it more quickly than the primary memory. It holds the data and programs frequently used by the CPU.
- Primary memory: a) RAM: It is a volatile memory. It means it does not store data or instructions permanently. When you switch on the computer the data and instructions from the hard disk are stored in RAM. b) ROM: It is a non-volatile memory. It means it does not lose its data or programs that are written on it at the time of manufacture. So it is a permanent memory that contains all important data and instructions needed to perform important tasks like the boot process.
- Secondary memory: The storage devices in the computer or connected to the computer are known as secondary memory of the computer. It is non-volatile in nature so permanently stores the data even when the computer is turned off.
Computers can be broadly classified by their speed and computing power.
|1||PC (Personal Computer)||It is a single user computer system having moderately powerful microprocessor|
|2||WorkStation||It is also a single user computer system which is similar to personal computer but have more powerful microprocessor.|
|3||Mini Computer||It is a multi-user computer system which is capable of supporting hundreds of users simultaneously|
|4||Main Frame||It is a multi-user computer system which is capable of supporting hundreds of users simultaneously. Software technology is different from minicomputer.|
|5||Supercomputer||It is an extremely fast computer which can execute hundreds of millions of instructions per second.|