Computer & Main Parts of Computer – Generation, Classification and Networks of Computers

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Generation of Computer

Generation of Computer
First Generation (1940 – 1956)Vacuum TubesMachine languageUNIVAC EDVAC
Second Generation (1956 – 1963)TransistorsAssembly languageIBM 1401
Third Generation (1964 – 1971)Integrated CircuitsHigh level languageIBM 360
Fourth Generation (1971 – Present)Microprocessors4GLPentium Series
Fifth Generation (Present & Beyond)Super large scale integrated chipsArtificial Intelligence (5GL)Robotics

Classification of Computers

Classification on Working System

  • Digital computer: digital computer is the most commonly used type of computer and is used to process information with quantities using digits, usually using the binary number system. Ex - MacBook.
  • Analog Computer: a computer that operates with numbers represented by directly measurable quantities (as voltages or rotations) — compare digital computer, hybrid computer.
  • Hybrid Computer: a computer that combines the characteristics of a digital computer and an analog computer by its capacity to accept input and provide output in either digital or analog form and to process information digitally.

Classification on Size

  • Mainframe computer: A mainframe computer is a very large computer capable of handling and processing very large amounts of data quickly. They are used by large institutions, such as government agencies and large corporations.
  • Mini Computer: a computer with processing and storage capabilities smaller than those of a mainframe but larger than those of a microcomputer.
  • Microcomputer:- A microcomputer is a complete computer on a smaller scale and is generally a synonym for the more common term, personal computer or PC , a computer designed for an individual.
  • Personal computer:- A personal computer (PC) is a small, relatively inexpensive computer designed for an individual user. In price, all are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip.
  • Supercomputers: The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of calculations.

Networking and Internet

Computer Networking

A computer network is a set of connected computers. Computers on a network are called nodes. The connection between computers can be done via cabling, most commonly the Ethernet cable, or wirelessly through radio waves. Connected computers can share resources, like access to the Internet, printers, file servers, and others.


  • Server: a computer designed to process requests and deliver data to other (client) computers over a local network or the Internet.
  • Receiver: a hardware module or device used to receive signals
  • Channel: physical connection between Server & Receiver

Transmission Channel

  • Simplex channels: simplex is a communications channel that operates in one direction at a time.
  • Half duplex channel:- A half-duplex channel can send and receive data, but not at the same time.
  • Full duplex channel:- Refers to the transmission of data in two directions simultaneously.

Types Data Communication Medium

  • Standard Telephone Line
  • Co-Axial Cable
  • Microwave Tranmission
  • Satellite Communication
  • Optical Fibers

Network Devices

  • Network adapter is a device that enables a computer to connect with another computer/network using MAC Address
  • Hub is a device that splits a network connection into multiple computers
  • Switch is a telecommunication device grouped as one of computer network components
  • Cable is one way of transmission media which can transmit communication signals.
  • Repeaters are used to regenerate or replicate signals that are weakened or distorted by transmission over long distances.
  • Bridge is used two connect two LANs with the same standard but using different types of cables.
  • Routers are used to join multiple computer networks together via either wired or wireless connections.
  • Gateways are a key stopping point for data on its way to or from other networks.
  • MODEM - Modulator-demodulator. Electronic device that allows computers to communicate over telephone wires or cable-TV cable.

Types of Network

  • Local Area Network (LAN) - a computer network that links devices within a building or group of adjacent buildings. Ex – Star LAN, Ring LAN, Bus LAN
  • Wide Area Network (WAN) - a computer network in which the computers connected may be far apart.
  • Metropolitan Area Network (MAN) - A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a LAN but smaller than the area covered by WAN. Ex- Public Networks Public Switched Telephone Networks (PSTN) Public Service Digital Network (PSDN)
  • Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data Network

Network Topology

  • Mesh topology - Mesh is a network topology in which devices are connected with many redundant interconnections between network nodes.
  • Star topology - Star topology is a network topology where each individual piece of a network is attached to a central node.
  • Ring topology - Ring topology refers to a specific kind of network setup in which devices are connected in a ring and pass information to each other according to their adjacent in the ring structure.
  • Bus topology - Bus topology is a specific kind of network topology in which all of the various devices in the network are connected to a single cable or line.
  • Tree topology – It is a combination characteristic of linear bus and star topologies.


OSI: The Open Systems Interconnection model (OSI Model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard of their underlying internal structure and technology.

Seven Layers of OSI Model

  • Physical layer - The physical layer is the first layer of the OSI Model that deals with bit-level transmission between different devices and supports electrical or mechanical interfaces connecting to the physical medium for synchronized communication.
  • Data Link Layer - The data link layer is the second layer of OSI model. This layer is the protocol layer that transfers data in the form of frames between adjacent network nodes in a wide area network or between nodes on the same local area network segment.
  • Network Layer - The network layer is the third level of the OSI Model and the layer that provides data routing paths for network communication. Data is transferred in the form of packets via logical network paths in an ordered format controlled by the network layer.
  • Transport Layer - The transport layer is the layer in the OSI model responsible for end-to-end communication (in the form of segments) over a network. It provides logical communication between application processes running on different hosts within a layered architecture of protocols and other network components.
  • Session Layer - In the OSI model, the session layer is the fifth layer, which controls the connections between multiple computers. The session layer tracks the dialogs between computers, which are also called sessions.
  • Presentation Layer - The presentation layer is layer 6 in OSI model. It is used to present data to the application layer (layer 7) in an accurate, well-defined and standardized format. The presentation layer is sometimes called the syntax layer.
  • Application Layer - The application layer is a layer in the OSI model and in the TCP/IP protocol suite. It consists of protocols that focus on process-to-process communication across an IP network and provides a firm communication interface and end-user services.

Data Transmission

  • NIC-Network interface card - A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network.
  • Wireless technology - Wireless communications is a type of data, a wireless signal through wireless communication technologies and device.