A computer is an advanced electronic device that takes raw data as input from the user and processes this data under the control of a set of instructions (called program) and gives the result (output) and saves output for future reference and usage.
The computer performs basically five major operations of functions irrespective of their size and make. These are
1) it accepts data or instruction by way of input,
2) it stores data,
3) it can process data as required by the user,
4) it gives results in the form of output, and
5) it controls all operations inside a computer. We discuss below each of these operations.
1.Input: this is the process of entering data and programs into the computer system. Ex: Keyboard , Mouse, Light Pen, Optical/magnetic Scanner , Touch Screen , Microphone for voice as input, Track Ball.
2. Control Unit (CU): The process of input, output, processing and storage is performed under the supervision of a unit called ‘Control Unit’. It decides when to start receiving data, when to stop it, where to store data, etc. It takes care of step -by-step processing of all operations inside the computer.
3. Memory Unit: Computer is used to store data and instructions.
4. Arithmetic Logic Unit (ALU): The major operations performed by the ALU are addition, subtraction, multiplication, division, logic and comparison.
5. Output: This is the process of producing results from the data for getting useful information. Ex . Monitor (Visual Display Unit) , Printers , Plotter, Speakers.
The ALU and the CU of a computer system are jointly known as the central processing unit (CPU). You may call the CPU as the brain of any computer system.
A. First Generation of Computers (1942-1959)
The beginning of the commercial computer age is from UNIVAC (Universal Automatic Computer). The first generation computers were used during 1942-1959. They were based on vacuum tubes. Examples of first generation computers are ENIAC and UNIVAC-1.
Advantages :
• Vacuum tubes were the only electronic component available during those days.
• Vacuum tube technology made it possible to make electronic digital computers.
• These computers could calculate data in milliseconds.
Disadvantages :
• The computers were very large in size.
• They consumed a large amount of energy.
• Non-portable.
• Limited commercial use.
• Very slow speed.
• Used machine language only.
• Used magnetic drums which provide very less data storage.
B. Second Generation Computers (1959-1965)
The second generation computers used transistors. The size of the computers was decreased by replacing vacuum tubes with transistors. The examples of second generation computers are IBM 7094 series, IBM 1400 series and CDC 1604 etc.
Advantages :
• Smaller in size as compared to the first generation computers.
• Used less energy and were not heated.
• Better speed and could calculate data in microseconds
• Used faster peripherals like tape drives, magnetic disks, printer etc.
• Used Assembly language instead of Machine language.
Disadvantages :
• Cooling system was required
• Constant maintenance was required
• Only used for specific purposes
• Costly and non-versatile
C. Third Generation Computers (1965-1975)
The Third generation computers used integrated circuits (IC). The first IC was invented and used in 1961. The size of an IC is about ¼ square inch. A single IC chip may contain thousands of transistors. The computers became smaller in size, faster, more reliable and less expensive. The examples of third generation computers are IBM 370, IBM System/360, UNIVAC 1108 and UNIVAC AC 9000 etc.
An integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated.
Advantages :
• Smaller in size as compared to previous generations.
• More reliable
Used less energy.
• Better speed and could calculate data in nanoseconds.
Disadvantages :
• Air conditioning was required.
• Highly sophisticated technology required for the manufacturing of IC chips.
D. Fourth Generation Computers (1975-1988)
The fourth generation of computers started with the invention of Microprocessor. The Microprocessor contains thousands of ICs. The LSI (Large Scale Integration) circuit and VLSI (Very Large Scale Integration) circuit was designed. It greatly reduced the size of the computer. The size of modern Microprocessors is usually one
square inch. It can contain millions of electronic circuits. The examples of fourth generation computers are Apple Macintosh & IBM PC.
Advantages :
• More powerful and reliable than previous generations.
• Small in size
• Microprocessors was started in use.
• Fast processing power with less power consumption
• Fan for heat discharging and thus to keep cold.
• Cheapest among all generations
• All types of High level languages C, C++ and Java can be used in this type of computers
Disadvantages :
• Very advanced technology was required to fabricate the ICs.
E. Fifth Generation Computers (1988 to Present)
Scientists are working hard on the 5th generation computers with quite a few breakthroughs. It is based on the technique of Artificial Intelligence (AI). Computers can understand spoken words & imitate human reasoning. IBM Watson computer is one example that outsmarts Harvard University Students.
ADVANTAGES
• Main electronic component: based on artificial intelligence, uses the Ultra Large-Scale Integration (ULSI) technology and parallel processing method.
o ULSI – millions of transistors on a single microchip
o Parallel processing method – use two or more microprocessors to run tasks simultaneously.
• Language – understand natural language (human language).
• Power – consume less power and generate less heat.
• Speed – remarkable improvement of speed, accuracy and reliability (in comparison with the fourth generation computers).
• Size – portable and small in size, and have a huge storage capacity.
• Input / output device – keyboard, monitor, mouse, trackpad (or touchpad), touchscreen, pen, speech input (recognize voice / speech), light scanner, printer, etc.
• Example – desktops, laptops, tablets, smartphones, etc.
TYPES OF COMPUTERS
1. Based on Size
| Type | Description | Examples |
|---|---|---|
| Supercomputer | Most powerful and fastest; used for weather forecasting, scientific simulations | PARAM, Summit, Fugaku |
| Mainframe Computer | Large systems that handle many users simultaneously; used in banks, airlines | IBM Z Series |
| Mini Computer | Smaller than mainframes but still support multiple users; used in mid-sized companies | PDP-11, VAX |
| Microcomputer | Single-user computers; most commonly used | Desktop, Laptop, Tablets, Smartphones |
2. Based on Purpose
| Type | Description | Examples |
|---|---|---|
| General Purpose | Can perform a variety of tasks | PCs, Laptops |
| Special Purpose | Designed for specific tasks | ATMs, Embedded systems, GPS |
3. Based on Functionality
| Type | Description |
|---|---|
| Analog Computer | Measures physical quantities like speed, temperature, pressure |
| Digital Computer | Performs calculations using binary digits (0 & 1) |
| Hybrid Computer | Combines analog and digital features |
4. Based on Data Handling
| Type | Description |
|---|---|
| Centralized Computer | All data is stored and processed in one system |
| Distributed Computer | Data is distributed across multiple systems connected through a network |
5. Portable Computers
| Type | Description |
|---|---|
| Laptop | Compact, portable personal computer |
| Notebook | Smaller and lighter than laptops |
| Tablet | Touch-screen device, portable, lightweight |
| Smartphone | Mobile device with computing capabilities |
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