Handout_Fundamentals of Computers

Fundamentals of ComputersIntroduction to ComputersAll devices that compute are called computers. Computers have a long history. They have traveled a long distance from primitiveness to sophistication. The abacus is the first manmade computing device that came into existence. After the abacus many devices came into existence one by one. In the general order of their invention, they are: Napier's Bones, the slide rule, Pascal' Calculator,Leibniz’s Calculator, Charles Babbage Difference Engine, Babbage's Analytical Engine, Hollerith Machine, Mark-1, Electronic Numerical Integrator and Computer (ENIAC), Electronic Discreet Variable Automatic Computer (EDVAC). We are currently in the era of modern computers. Each computer that was developed was smaller in size but faster in speed than its predecessor.Computers are basically dumb devices. They perform tasks according to the instructions given to them by the user. Their working capabilities are much beyond the capabilities of human beings. They can perform a task at very fast speeds for long durations without making any mistake.Computers that are developed during a specific electronic era are often referred to as “a generation.” All together, there have been four generations of computers. First generation computers were made using vacuum tubes. Second generation computer were made using transistors. Computers that were designed with simple integrated circuits were called third generation computers. Current generation computers are fourth generation computers and use very large scale integrated circuits (VLIC). Computers that have thinking power will come in the future and are often referred to as fifth generation computers.On the basis of the input that computers accept, they have been classified into three categories:1. Analog computers2. Digital Computers3. Hybrid computersThose computers that take signals as input are called analog computers. Computers that accept digits as input are called digital computers. Computers that accept both signals and digits are called hybrid computers. The computers that we usually see in offices, schools, colleges, etc., are digital computers. Digital computers are classified into the following categories:1. Microcomputers2. Mini computers3. Mainframe computers4. SupercomputersThe microcomputer is the smallest category of computers and supercomputer is the largest.The physical parts of the computer that can be seen or touched are called hardware. Hardware doesn't function on its own. It requires instructions to work. The instructions that make hardware work are called software.Software is broadly classified into following two categories:System SoftwareApplication SoftwareInstructions that are used to start up the computer or to manage the computer’s resour ces are called system software.Instructions that are given to computers for automating manual tasks are called application software. Instructions that cause the computer to perform a specific task is called program.The computer is mainly used for data processing. Raw facts and figures are called data. Once data is processed, it is called information. When information is understood and used in new ways, it is wisdom. Computer OrganizationThe computer is an electronic device. The computer consists of many devices, as shown below:Those devices that allow us to enter into the computer data or instructions are called input units. The keyboard, mouse, CD-ROM drive, etc. are common input devices.Those devices that provide the results of processing are called output devices. The screen, printer, etc. are common output devices.Those devices that store data permanently are called input / output devices - they perform both input and output functions. Floppy drives, hard disk, magnetic tape drive, cartridge tape drive,and CD-writer are few examples of Input / Output devices. They are called storage.The Arithmetic and Logic Unit (ALU) of the computer performs all arithmetic and logical operations. The Control Unit ensures movement of the right data from the right source to the right destination at the right time. The Control Unit allows all the units of the computer to perform their functions in coordination with each other.MemorySome data and instructions are kept in the computer only so long as the computer is turned on. This is called temporary memory. There are two kinds of temporary memory:1. Primary Memory2. Cache MemoryThe memory that is used by the computer for its internal functioning is called primary memory. There are two types of primary memory:1. Read Only Memory (ROM)2. Random Access Memory (RAM)Sometimes the computer can only read instructions. This type of memory is called Read Only Memory (ROM). Sometimes the computer can both read and write instructions and temporarily store data; this type of memory is called Random Access Memory. The computer can read from or write to any part of RAM.Cache memory is fast memory. Its purpose is to increase the speed of the computer. It is located between the processor and RAM. If it is available, the computer performs all its read / write operations in cache. Later the computer may transfer part or all of its cache memory to RAM.Operating SystemThe operating system is the most essential software for the functioning of computer. Without an operating system, the computer cannot work. It starts all the parts of computer and makes it possible to execute commands from users.Before starting any work on computer, the operating system has to be loaded in computer's memory. The process of loading the operating system in computer's memory is called booting.The responsibilities of the operating system are:1. Performing internal management functions.2. Providing services.3. Providing user interface.The operating system performs the following internal management functions:1. Process management2. Memory management3. Information management4. Device managementUsing the interface, the user interacts with computer. Generally there are two types of interfaces:1. Command Line Interface (CLT).2. Graphical User Interface (GUI).In the command line interface, the user interacts with computer through text commands; in graphical user interface s/he interacts through picture objects like icons, menus, dialog boxes etc..Operating systems can be broadly classified into following categories:1. Single user operating systems: allows only one user to work on the system at a time. MS-DOS & Windows are examples.2. Multi-user operating systems: allows many users to work on the system at the same time. Linux & UNIX are examples.3. Network operating system: includes special functions, protocols and device drivers for connecting the computers of the network. Windows-NT, Windows-2000 & Windows-3000 are examples.Computer CommunicationWhen two or more computers are connected together with the objective of communicating with each other and sharing their resources, they form a computer network.Using computer networks, fast and reliable communication takes place. Networks allow people to: networking:1. Share distant devices2. Share software3. Communicate4. Evenly distribute the load of processingTypes of NetworksComputer networks are broadly classified into two categories:Local Area Networks (LAN): Local area networks are the networks that spread within a short distance of a kilometer or so and are generally confined to a building or a campus.Wide Area Networks (WAN): Wide Area Networks or WAN are the networks, in which computers are spread over long distances (more than a kilometer). For example, networks that connect computer in different in different countries, cities or localities.Topology is the physical arrangement of computers in the network. There are various topologies including the bus topology, ring topology, star topology, and mesh topology.The basic network communication system consists of the following parts:Sender: The computer that sends a message is called the sender.Receiver: That computer that receives the message is called the receiver.Medium: The medium is that material through which the message travels to its destination. The medium can be wired (twisted pair cable, coaxial cable, or optic fiber cable) or non-wired where messages travel through the air.Message: The text, sound or images that travel from the sender to the receiver is called the message. Protocol: A set of standards for communication between the sender and receiver.Data transmission is the sending of any kind of information from one place to other. There are two types of data transmission: analog transmission and digital transmission.There are two transmission techniques: asynchronous and synchronous transmission.In asynchronous transmission, data is sent and received one byte at a time. In synchronous transmission all the data is sent at once. Synchronous transmission is significantly faster.The way the message travels along the transmission line is called the mode of transmission. There are three modes of transmission:Simplex mode: In this mode, data is transmitted in one direction only.Half duplex mode: In this mode, data is transmitted in both directions but not simultaneously.Full duplex mode: In this mode, the transmission line sends and receives data in both directions at the same time.The InternetThe Internet is a network of computer networks. It extends all across the globe. Computers on the Internet are:Servers: Those computers that provide data and services to other computers. They are generally fast computers and remain connected to the Internet all the time.Clients: Those computers that take data and services from other computers. They are generally slow computers and get connected to Internet when they require services from the servers.Computers on the Internet are identified by a unique address, called IP address. An IP address consists of four numbers separated by dots (.). For example 024.136.225.128 is an IP address. They are also identified by a unique name, called a domain name.That part of the Internet that uses Hyper Text Transfer Protocol (http) to make multimedia media objects appear on Internet is called the World Wide Web. E-mail, video conferencing, chatting, Internet telephony, on-line shopping, banking, and searching are few popular uses of Internet.。