A motor within the CD player rotates the disk. The capacity of an ordinary CD- ROM is 700MB. Fig . Compact Disc .
. Digital Versatile Disc (DVD) A DVD (Digital Versatile Disc or Digital Video Disc) is an optical disc capable of storing up to . GB of data, more than six times what a CD can hold. DVDs are often used to store movies at a better quality.
Like CDs, DVDs are read with a laser. The disc can have one or two sides, and one or two layers of data per side; the number of sides and layers determines how much it can hold. Double-layered sides are usually gold-coloured, while single-layered sides are usually silver-coloured, like a CD. Fig .
Digital Versatile Disc . . Flash Memory Devices Flash memory is an electronic (solid-state) non-volatile computer storage medium that can be electrically erased and reprogrammed. They are either EEPROM or EPROM.
Examples for Flash memories are pendrives, memory cards etc. Flash memories can be used in personal computers, Personal Digital Assistants (PDA), digital audio players, digital cameras and mobile phones. Flash memory offers fast access times. The time taken to read or write a character in memory is called access time.
The capacity of the flash memories vary from Gigabytes (GB) to Terabytes (TB). A sample of flash memory is shown in Figure . . Figure .
Flash Memory . . Blu-Ray Disc Blu-Ray Disc is a high-density optical disc similar to DVD. Blu-ray is the type of disc used for PlayStation games and for playing High-Definition (HD) movies.
A double-layer Blu-Ray disc can store up to 50GB (gigabytes) of data. DVD uses a red laser to read and write data. But, Blu-ray uses a blue-violet laser to write. Hence, it is called as Blu-Ray.
Fig . Blu- Ray Disc . Ports and Interfaces The Motherboard of a computer has many I/O sockets that are connected to the ports and interfaces found on the rear side of a computer (Figure . ).
The external devices can be connected to the ports and interfaces. The various types of ports are given