MODEM

A modem is a device that lets you connect your computer to a standard telephone line or cable  so that you can transmit, and receive electronically transmitted data.

A USB wireless Modem

It is the keys that unlocks the world of the internet and its world wild web. The goal is to produce a signal that can transmitted easily, and decoded to produce the original digital data. The modem converts a computer’s digital signals into specific frequencies to travel over telephone or cable television lines. At the destination, the receiving modem demodulates the frequencies back into digital data.The word modem is a blend of ‘modulator’ and ‘demodulator’.

CDs very useful

CDs or compact discs are optical discs used to store digital data. During their manufacture, this disc is etched with microscopic bumps, arranged as a single, continuous, extremely long spiral track. The bumps store the data in a coded form.

   

             The surface of a CD is reflective because the disc is coated with a thin layer of aluminum. The shiny metal layer reflects the laser that is used to read or write the device. A layer of lacquer is then spin-coated onto the CD to protect the metal.

              Since nothing touches the encoded portion, the CD is not worn out during use, which makes them very useful for storing information.

GRAPHICAL USER INTERFACE

Graphical User Interface of Windows 95

The Xerox Alto the first computer to use a GUI

Computers have to be told what to do- and there was a time when this was done with index cards, called punch    cards, that had holes punched in them, latter, text commands were used to instruct computers. These methods of communicating with your computer have been replaced with the graphical user interface. A graphical user interface or GUI is a way for humans to interact with computer windows, icons, and menus.

                          A windows is a rectangular portion of the monitor screen that can display its contents. An icon is a small picture or symbol in GUI that represents a program a directory or device like a hard disk. Commands are issued in the GUI by using a mouse, trackball, or touchpad to move a pointer on the screen.

            

Hard Disc Drive

Your computer’s hard disc drive is a device for storing and retrieving digital information.

The hard disc drive was first introduced by IBM in 1956.