1/11/2021
Computer notes 2 - GKmojo
GKmojo
Protected: Computer notes 2
Computer Bullet Points
1. 1st Computer in India was installed in the main post office of Bangalore on August 16, 1986.
2. Bangalore is also known as Silicon Valley of India.
3. 1st Indian magazine to be available on Internet is ‘India Today’.
4. Most Super computer use- Linux.
5. FORTRAN is the first Programming language.
6. PROLOG is the language of the fifth generation of computer.
7. A computer error is known as Bug.
8. Laser printers are the fasted printers.
9. Indian Super computer PARAM-10000 is developed C-DAC Pune.
10. Speed of computer is measured in Hertz (Hz).
Important Computer Extensions
Text Files
.log: Log File
.doc: Microsoft Word Document
.docx: Microsoft Word Open XML Document
.msg: Outlook Mail Message
.rtfRich: Text Format File
Data Files
.dat: Data File
.pptx: Power Point Open XML Presentation
.xml: XML File
.pps: Power Point Slide Show
.ppt: Power Point Presentation
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Audio Files
.aif: Audio Interchange File Format
.mpa: MPEG-2 Audio File
.ra: Real Audio File
.iff: Interchange File Format
.wav: WAVE Audio File
.mp3: MP3 Audio File
Video Files
.avi: Audio Video Interleave File
.flv: Flash Video File
.mpg: MPEG Video File
.vob: DVD Video Object File
.mp4: MPEG-4 Video File
.wmv: Windows Media Video File
Networks Devices
A network device refers to a component that is used to connect computers in a network. The following
are some commonly used network devices:
Repeater: It is a two-port signal regenerator that is used to extend the length of an Ethernet cable. It
produces the original bit pattern for the attenuated signal it receives. It works at the physical
layer.
Bridge: It connects two or more LANs. It operates at both physical and data link layers to regenerate
the input signals and filter the frames respectively. It filters frames on the basis of a table containing
MAC addresses of every node and the port number. It checks for the MAC addresses of the source and
destination node contained in a frame and decides or forwarding or dropping the frame.
Hub: It contains several ports for connecting multiple computers to form a small network.
A simple hub is also called concentrator. It works at the physical layer of OSI model where it
connects several segments of a LAN together or multiple workstations in a single LAN.
Switch: It connects two network segments as well as various LANs and WANs together
Router: It connects two networks together and ensures routing of data between nodes and networks.
A router has a routing table containing source and destination addresses. On receiving a data packet,
the router seeks the destination address from the routing table and ensures the best route of data
around network. Having data that, it proceeds to forward the data packet to its appropriate
destination. It works on the network layer of OSI Model.
Gateway: It connects more than one network that uses different protocols. It mainly works at the
network layer. Gateways, also called protocol converters.
Modem: It is a hardware device used to send and receive data over a transmission medium, usually
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telephone lines. The first modem was introduced in 1960 AT&T Corporation of the US. AT&T
designed its Dataphone, the first commercial modem, specifically for converting digital computer data
to analog signals for transmission across its long distance network.
Input Unit
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The input device or input unit of the computer system is used for feeding data and instructions to the
computer. An input device allows users to communicate and feed instructions and data to computers
for processing, display, storage and/or transmission.
Keyboards: Allow users to input alphanumeric data and commands
Pointing devices and game controllers: Allow users to direct application software and interact
with graphical user interfaces
Audio and video devices: Allow users to capture sound and images
Output Unit
An output device or output unit is used to send data from a computer to another device or user. A
display device is an output device that visually conveys text, graphics, and video information.
Examples of an output device include monitors, projectors, speakers, headphones and printers.
Input/output Unit
Devices for communication between computers, such as modems and network cards, typically
perform both input and output operations such devices are termed as Input/output Units or devices.
The touchscreen is also a popular example of such devices.
Central Processing Unit
The Central Processing Unit (CPU) is the computer component that’s responsible for interpreting and
executing most of the commands from the computer’s other hardware and software. A CPU is further
categorised into following parts for a simple and basic understanding of its functioning:
1) Arithmetic-Logic unit
2) Control Unit
3) Memory Unit
Arithmetic-Logic Unit (ALU): The ALU is an electronic circuit used to carry out the arithmetic
operations like addition, subtraction, multiplication and division. This unit carries out logical
operations like greater than, less than, equal to etc. It performs the operation on the data provided the
input devices.
Control Unit: The control unit coordinates the activities of all the other units in the system. Its main
functions are to control the transfer of data and information between various units and to initiate
appropriate actions the arithmetic-logic unit. Conceptually, the control unit fetches instructions from
the memory, decodes them, and directs them to various units to perform the specified tasks.
Memory Unit: The main memory is also called primary memory, is used to store data temporarily.
Although the CPU is the brain behind all the operations in the computer, it needs to be supplied with
the data to be processed and the instructions to tell it what to do. Once the CPU has carried out an
instruction, it needs the result to be stored. This storage space is provided the computer’s memory.
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