1. Basic Introduction of computer

Microprocessor concepts

Microprocessor is the brain of computer, which does all the work. It is a computer processor that incorporates all the functions of CPU (Central Processing Unit) on a single IC (Integrated Circuit) or at the most a few ICs. Microprocessors were first introduced in early 1970s. 4004 was the first general purpose microprocessor used by Intel in building personal computers. Arrival of low cost general purpose microprocessors has been instrumental in development of modern society the way it has.


We will study the characteristics and components of a microprocessor in detail.

Microprocessors Characteristics

Microprocessors are multipurpose devices that can be designed for generic or specialized functions. The microprocessors of laptops and smartphones are general purpose whereas ones designed for graphical processing or machine vision are specialized ones. There are some characteristics that are common to all microprocessors.

These are the most important defining characteristics of a microprocessor −

  • Clock speed
  • Instruction set
  • Word size

Clock Speed

Every microprocessor has an internal clock that regulates the speed at which it executes instructions and also synchronizes it with other components. The speed at which the microprocessor executes instructions is called clock speed. Clock speeds are measured in MHz or GHz where 1 MHz means 1 million cycles per second whereas 1 GHz equals to 1 billion cycles per second. Here cycle refers to single electric signal cycle.

Currently microprocessors have clock speed in the range of 3 GHz, which is maximum that current technology can attain. Speeds more than this generate enough heat to damage the chip itself. To overcome this, manufacturers are using multiple processors working in parallel on a chip.

Word Size

Number of bits that can be processed by a processor in a single instruction is called its word size. Word size determines the amount of RAM that can be accessed at one go and total number of pins on the microprocessor. Total number of input and output pins in turn determines the architecture of the microprocessor.

First commercial microprocessor Intel 4004 was a 4-bit processor. It had 4 input pins and 4 output pins. Number of output pins is always equal to the number of input pins. Currently most microprocessors use 32-bit or 64-bit architecture.

Instruction Set

A command given to a digital machine to perform an operation on a piece of data is called an instruction. Basic set of machine level instructions that a microprocessor is designed to execute is called its instruction set. These instructions do carry out these types of operations −

  • Data transfer
  • Arithmetic operations
  • Logical operations
  • Control flow
  • Input/output and machine control

Microprocessor Components

Compared to the first microprocessors, today’s processors are very small but still they have these basic parts right from the first model −

  • CPU
  • Bus
  • Memory


CPU is fabricated as a very large scale integrated circuit (VLSI) and has these parts −

  • Instruction register − It holds the instruction to be executed.
  • Decoder − It decodes (converts to machine level language) the instruction and sends to the ALU (Arithmetic Logic Unit).
  • ALU − It has necessary circuits to perform arithmetic, logical, memory, register and program sequencing operations.
  • Register − It holds intermediate results obtained during program processing. Registers are used for holding such results rather than RAM because accessing registers is almost 10 times faster than accessing RAM.


Connection lines used to connect the internal parts of the microprocessor chip is called bus. There are three types of buses in a microprocessor −

  • Data Bus − Lines that carry data to and from memory are called data bus. It is a bidirectional bus with width equal to word length of the microprocessor.
  • Address Bus − It is a unidirectional responsible for carrying address of a memory location or I/O port from CPU to memory or I/O port.
  • Control Bus − Lines that carry control signals like clock signals, interrupt signal or ready signal are called control bus. They are bidirectional. Signal that denotes that a device is ready for processing is called ready signal. Signal that indicates to a device to interrupt its process is called an interrupt signal.


Microprocessor has two types of memory

  • RAM − Random Access Memory is volatile memory that gets erased when power is switched off. All data and instructions are stored in RAM.
  • ROM − Read Only Memory is non-volatile memory whose data remains intact even after power is switched off. Microprocessor can read from it any time it wants but cannot write to it. It is preprogrammed with most essential data like booting sequence by the manufacturer.
1. Basic Introduction of computer

Office Tools

Application software that assist users in regular office jobs like creating, updating and maintaining documents, handling large amounts of data, creating presentations, scheduling, etc. are called office tools. Using office tools saves time and effort and lots of repetitive tasks can be done easily. Some of the software that do this are −

  • Word processors
  • Spreadsheets
  • Database systems
  • Presentation software
  • E-mail tools

Let us look at some of these in detail.

Word Processor

A software for creating, storing and manipulating text documents is called word processor. Some common word processors are MS-Word, WordPad, WordPerfect, Google docs, etc.

Word Processor

A word processor allows you to −

  • Create, save and edit documents
  • Format text properties like font, alignment, font color, background color, etc.
  • Check spelling and grammar
  • Add images
  • Add header and footer, set page margins and insert watermarks


Spreadsheet is a software that assists users in processing and analyzing tabular data. It is a computerized accounting tool. Data is always entered in a cell (intersection of a row and a column) and formulas and functions to process a group of cells is easily available. Some of the popular spreadsheet software include MS-Excel, Gnumeric, Google Sheets, etc. Here is a list of activities that can be done within a spreadsheet software −

  • Simple calculations like addition, average, counting, etc.
  • Preparing charts and graphs on a group of related data
  • Data entry
  • Data formatting
  • Cell formatting
  • Calculations based on logical comparisons

Presentation Tool

Presentation tool enables user to demonstrate information broken down into small chunks and arranged on pages called slides. A series of slides that present a coherent idea to an audience is called a presentation. The slides can have text, images, tables, audio, video or other multimedia information arranged on them. MS-PowerPoint, OpenOffice Impress, Lotus Freelance, etc. are some popular presentation tools.

Presentation Tool

Database Management System

Software that manages storage, updating and retrieval of data by creating databases is called database management system. Some popular database management tools are MS-Access, MySQL, Oracle, FoxPro, etc.

Database Management System
1. Basic Introduction of computer

Software Concepts

As you know, the hardware devices need user instructions to function. A set of instructions that achieve a single outcome are called program or procedure. Many programs functioning together to do a task make a software.

For example, a word-processing software enables the user to create, edit and save documents. A web browser enables the user to view and share web pages and multimedia files. There are two categories of software −

  • System Software
  • Application Software
  • Utility Software

Let us discuss them in detail.

System Software

System Software

Software required to run the hardware parts of the computer and other application software are called system software. System software acts as interface between hardware and user applications. An interface is needed because hardware devices or machines and humans speak in different languages.

Machines understand only binary language i.e. 0 (absence of electric signal) and 1 (presence of electric signal) while humans speak in English, French, German, Tamil, Hindi and many other languages. English is the pre-dominant language of interacting with computers. Software is required to convert all human instructions into machine understandable instructions. And this is exactly what system software does.

Based on its function, system software is of four types −

  • Operating System
  • Language Processor
  • Device Drivers

Operating System

System software that is responsible for functioning of all hardware parts and their interoperability to carry out tasks successfully is called operating system (OS). OS is the first software to be loaded into computer memory when the computer is switched on and this is called booting. OS manages a computer’s basic functions like storing data in memory, retrieving files from storage devices, scheduling tasks based on priority, etc.

Language Processor

As discussed earlier, an important function of system software is to convert all user instructions into machine understandable language. When we talk of human machine interactions, languages are of three types −

  • Machine-level language − This language is nothing but a string of 0s and 1s that the machines can understand. It is completely machine dependent.
  • Assembly-level language − This language introduces a layer of abstraction by defining mnemonicsMnemonics are English like words or symbols used to denote a long string of 0s and 1s. For example, the word “READ” can be defined to mean that computer has to retrieve data from the memory. The complete instruction will also tell the memory address. Assembly level language is machine dependent.
  • High level language − This language uses English like statements and is completely independent of machines. Programs written using high level languages are easy to create, read and understand.

Program written in high level programming languages like Java, C++, etc. is called source code. Set of instructions in machine readable form is called object code or machine codeSystem software that converts source code to object code is called language processor. There are three types of language interpreters−

  • Assembler − Converts assembly level program into machine level program.
  • Interpreter − Converts high level programs into machine level program line by line.
  • Compiler − Converts high level programs into machine level programs at one go rather than line by line.

Device Drivers

System software that controls and monitors functioning of a specific device on computer is called device driver. Each device like printer, scanner, microphone, speaker, etc. that needs to be attached externally to the system has a specific driver associated with it. When you attach a new device, you need to install its driver so that the OS knows how it needs to be managed.

Application Software

A software that performs a single task and nothing else is called application software. Application software are very specialized in their function and approach to solving a problem. So a spreadsheet software can only do operations with numbers and nothing else. A hospital management software will manage hospital activities and nothing else. Here are some commonly used application software −

  • Word processing
  • Spreadsheet
  • Presentation
  • Database management
  • Multimedia tools

Utility Software

Application software that assist system software in doing their work is called utility software. Thus utility software is actually a cross between system software and application software. Examples of utility software include −

  • Antivirus software
  • Disk management tools
  • File management tools
  • Compression tools
  • Backup tools
1. Basic Introduction of computer

Basic Classification of Computer

Historically computers were classified according to processor types because development in processor and processing speeds were the developmental benchmarks. Earliest computers used vacuum tubes for processing, were huge and broke down frequently. However, as vacuum tubes were replaced by transistors and then chips, their size decreased and processing speeds increased manifold.

All modern computers and computing devices use microprocessors whose speeds and storage capacities are skyrocketing day by day. The developmental benchmark for computers is now their size. Computers are now classified on the basis of their use or size −

  • Desktop
  • Laptop
  • Tablet
  • Server
  • Mainframe
  • Supercomputer

Let us look at all these types of computers in detail.


Desktop computers are personal computers (PCs) designed for use by an individual at a fixed location. IBM was the first computer to introduce and popularize use of desktops. A desktop unit typically has a CPU (Central Processing Unit), monitor, keyboard and mouse. Introduction of desktops popularized use of computers among common people as it was compact and affordable.


Riding on the wave of desktop’s popularity many software and hardware devices were developed specially for the home or office user. The foremost design consideration here was user friendliness.


Despite its huge popularity, desktops gave way to a more compact and portable personal computer called laptop in 2000s. Laptops are also called notebook computers or simply notebooks. Laptops run using batteries and connect to networks using Wi-Fi (Wireless Fidelity) chips. They also have chips for energy efficiency so that they can conserve power whenever possible and have a longer life.


Modern laptops have enough processing power and storage capacity to be used for all office work, website designing, software development and even audio/video editing.


After laptops computers were further miniaturized to develop machines that have processing power of a desktop but are small enough to be held in one’s palm. Tablets have touch sensitive screen of typically 5 to 10 inches where one finger is used to touch icons and invoke applications.


Keyboard is also displayed virtually whenever required and used with touch strokes. Applications that run on tablets are called apps. They use operating systems by Microsoft (Windows 8 and later versions) or Google (Android). Apple computers have developed their own tablet called iPad which uses a proprietary OS called iOS.


Servers are computers with high processing speeds that provide one or more services to other systems on the network. They may or may not have screens attached to them. A group of computers or digital devices connected together to share resources is called a network.


Servers have high processing powers and can handle multiple requests simultaneously. Most commonly found servers on networks include −

  • File or storage server
  • Game server
  • Application server
  • Database server
  • Mail server
  • Print server


Mainframes are computers used by organizations like banks, airlines and railways to handle millions and trillions of online transactions per second. Important features of mainframes are −

  • Big in size
  • Hundreds times Faster than servers, typically hundred megabytes per second
  • Very expensive
  • Use proprietary OS provided by the manufacturers
  • In-built hardware, software and firmware security features


Supercomputers are the fastest computers on Earth. They are used for carrying out complex, fast and time intensive calculations for scientific and engineering applications. Supercomputer speed or performance is measured in teraflops, i.e. 1012 floating point operations per second.


Chinese supercomputer Sunway TaihuLight is the world’s fastest supercomputer with a rating of 93 petaflops per second, i.e. 93 quadrillion floating point operations per second.

Most common uses of supercomputers include −

  • Molecular mapping and research
  • Weather forecasting
  • Environmental research
  • Oil and gas exploration
1. Basic Introduction of computer


Starting a computer or a computer-embedded device is called booting. Booting takes place in two steps −

  • Switching on power supply
  • Loading operating system into computer’s main memory
  • Keeping all applications in a state of readiness in case needed by the user

The first program or set of instructions that run when the computer is switched on is called BIOS or Basic Input Output System. BIOS is a firmware, i.e. a piece of software permanently programmed into the hardware.

If a system is already running but needs to be restarted, it is called rebooting. Rebooting may be required if a software or hardware has been installed or system is unusually slow.

There are two types of booting −

  • Cold Booting − When the system is started by switching on the power supply it is called cold booting. The next step in cold booting is loading of BIOS.
  • Warm Booting − When the system is already running and needs to be restarted or rebooted, it is called warm booting. Warm booting is faster than cold booting because BIOS is not reloaded.
1. Basic Introduction of computer

Characteristics of Computer

To understand why computers are such an important part of our lives, let us look at some of its characteristics −

  • Speed − Typically, a computer can carry out 3-4 million instructions per second.
  • Accuracy − Computers exhibit a very high degree of accuracy. Errors that may occur are usually due to inaccurate data, wrong instructions or bug in chips – all human errors.
  • Reliability − Computers can carry out same type of work repeatedly without throwing up errors due to tiredness or boredom, which are very common among humans.
  • Versatility − Computers can carry out a wide range of work from data entry and ticket booking to complex mathematical calculations and continuous astronomical observations. If you can input the necessary data with correct instructions, computer will do the processing.
  • Storage Capacity − Computers can store a very large amount of data at a fraction of cost of traditional storage of files. Also, data is safe from normal wear and tear associated with paper.
1. Basic Introduction of computer


Being a modern-day kid you must have used, seen, or read about computers. This is because they are an integral part of our everyday existence. Be it school, banks, shops, railway stations, hospital or your own home, computers are present everywhere, making our work easier and faster for us. As they are such integral parts of our lives, we must know what they are and how they function. Let us start with defining the term computer formally.

The literal meaning of computer is a device that can calculate. However, modern computers can do a lot more than calculate. Computer is an electronic device that receives input, stores or processes the input as per user instructions and provides output in desired format.

Input-Process-Output Model

Computer input is called data and the output obtained after processing it, based on user’s instructions is called information. Raw facts and figures which can be processed using arithmetic and logical operations to obtain information are called data.


The processes that can be applied to data are of two types −

  • Arithmetic operations − Examples include calculations like addition, subtraction, differentials, square root, etc.
  • Logical operations − Examples include comparison operations like greater than, less than, equal to, opposite, etc.

The corresponding figure for an actual computer looks something like this −

Block Diagram

The basic parts of a computer are as follows −

  • Input Unit − Devices like keyboard and mouse that are used to input data and instructions to the computer are called input unit.
  • Output Unit − Devices like printer and visual display unit that are used to provide information to the user in desired format are called output unit.
  • Control Unit − As the name suggests, this unit controls all the functions of the computer. All devices or parts of computer interact through the control unit.
  • Arithmetic Logic Unit − This is the brain of the computer where all arithmetic operations and logical operations take place.
  • Memory − All input data, instructions and data interim to the processes are stored in the memory. Memory is of two types – primary memory and secondary memory. Primary memory resides within the CPU whereas secondary memory is external to it.

Control unit, arithmetic logic unit and memory are together called the central processing unit or CPU. Computer devices like keyboard, mouse, printer, etc. that we can see and touch are the hardware components of a computer. The set of instructions or programs that make the computer function using these hardware parts are called software. We cannot see or touch software. Both hardware and software are necessary for working of a computer.