A Computer is an electronic device that can perform activities which involve mathematical computations, logical operations, and graphical manipulations. Generally, the term "Computer" is used to describe a collection of devices that function together as a system.It performs the following three operations in sequence:
A computer is a programmable electronic device(machine) that takes raw facts as input, process them and gives the final output which is the result of processing. It responds to a specific set of instructions in a well-defined manner. It can execute a prerecorded list of instructions (a program).
Data: It is the collection of raw facts, figures & symbols to be processed.Ex: Names of teachers and their salary in different subjects listed in random order.
Information: It is the data that is processed & presented in an organized manner. The processed data are known as information.Ex: When the names of students of a class are arranged in alphabetical order, total marks and average marks obtained are calculated & presented in a tabular form, it is the information.
Program: Set of instructions that enable a computer to perform a given specified task.
Characteristics of computers
High speed: Computers have the ability to perform routine tasks at a greater speed than humans. They can perform millions of calculations in few seconds.
Accuracy: Computers are used to perform tasks in such a way that ensures accuracy. Computers give accurate results as per the activities performed.
Storage: Computers can store a large amount of data & information. Any item of data or any instruction stored in the memory can be retrieved(again be used) by the computer at lightning speeds.
Automation: Computers can be instructed to perform complex tasks automatically (that increases the productivity).
Diligence: Computers can perform the same task repeatedly & with the same accuracy without getting tired or bored.
Versatility: Computers are flexible to perform both simple and complex tasks. So they are also called versatile machines.
Cost effectiveness: Computers reduce the amount of paperwork and human effort, thus reducing the costs.
Classification of Digital Computers (Types of Computers)
Computers can be classified by their size and power as drafted below:
These are also called PCs(Personal Computers). They are the smallest and least expensive category of general purpose computers. Microcomputer ranges from palmtops to Desktop computers in size. Laptops/ Notebooks are very popular nowadays. The microprocessor is the core part of the Microcomputers which forms the CPU.
A computer with minimal memory, disk storage and processor power designed to connect to a network, especially the Internet is a Network Computer. The idea behind network computers is that many users who are connected to a network do not need all the computer power they get from a typical PC(Personal Computer). Instead, they can rely on the power of the network servers. This is really a variation on an old idea -- diskless workstations -- which are computers that have memory and a processor but no any disk storage. Instead, they rely on a server to store data. Network computers take this idea one step further by also minimizing the amount of memory and processor power required by the workstation. Network computers designed to connect to the Internet are sometimes called Internet boxes, Net PCs, and Internet appliances.
The CPU is the “brain” of the computer, the place where data is manipulated. In larger computer systems, such as supercomputers and mainframe computers, processing task may be handled by multiple processing chips. In the average microcomputer, the entire CPU acts as a single unit called a microprocessor. Every CPU has at least two parts: the control unit (CU) and the arithmetic and logic unit (ALU).
The Control Unit (CU)
All the resources of the computer are managed by the control unit. The control unit controls the data flow through the CPU, and to and from other devices. The control unit is the logical hub of the computer.
The Arithmetic and Logic Unit (ALU)
Many instructions which are carried out by the CU involve simply moving data from one place to another from memory to storage, from memory to the printers and so on. When the control unit encounters an instruction that involves arithmetic or logic, however, it passes the instruction to the second components of the CPU, the arithmetic and logic unit or ALU. The ALU actually performs the arithmetic operations (+,-,X, ÷) and the logical operations (=,>,<,>=,<=,!= etc). The ALU includes a group of registers- high-speed memory locations built directly into the CPU that is used to hold data currently being processed.
In microcomputers, the term "bus" refers to the path between the various components of a computer. There are two main buses in a computer: the system (or internal) bus and the expansion ( or external) bus. The system bus resides on the motherboard and connects the CPU to other devices that reside on the motherboard. An expansion or external bus connects external devices, such as the keyboard, mouse, modem, printer etc to the CPU. Cables from disk drives and some other internal devices may also be plugged into the bus.
Functions and Components of a Computer:
In order to function properly, the computer needs both hardware and software. Hardware consists of the mechanical and electronic devices, which we can see and touch. The different parts of the computer are Processor (CPU), Input devices, Output devices, Storage devices and Memory devices. The software consists of programs, the operating systems(OS) and the data that reside in the memory and storage devices.Computer hardware falls into two categories: processing hardware, which consists of the central processing unit (CPU), and the peripheral devices. The CPU, as its name implies, is where the data processing is done. Peripheral devices allow the user to interact with the CPU. Together, they make it possible to use the computer for a variety of tasks.
A computer mainly does the following four functions:
Working of CPU and memory
An instruction is fetched from primary storage by the Control Unit(CU). The Control Unit decodes the instruction. The ALU receives the data and the instruction and performs the calculation or comparison. The result is stored in primary storage which is sent to the proper output device.