is volatile because its contents are erased when power is switched off. The other type of system memory is ROM Read only Memory which is permanent because it contents are not erased even when power is switched off. It is usually used to load an operating system.
8 Hard disk drive
Fig 1.1.7 Hard Disk Drive A hard drive consists of spinning platters made up of aluminum or ceramic that is coated with magnetic media. The platters come in various sizes. The hard drive with many different storage capacities can be created depending upon the density, size and number of platters. This is also called as Secondary memory. There can be several programs in the system, which cannot be stored in RAM, so we need a very huge nonvolatile memory, which can be used for storing all the programs, and data when the system is not in use are called as Hard disks. CD-ROM drive
Fig 1.1.8 CDROM Drive CD-ROM stands for compact disk read only memory. It consists of small disks similar to the gramophone records to hold digital information. As the name applies they are read only medium. With the advancement in technology writable CD s are also available. Floppy Disk Drive
Fig 1.1.9 Floppy Disk Drive Floppy disks are the slowest and the smallest form of secondary storage. They provide a simple way to carry information from one place to another, and backup small amount of files. In modern days floppy drive component is not as important as it was years ago. All PC s made in the last 10 years use a standard 3 inch, 1.44 MB capacity floppy drive.
Chapter 1 Fig 9 Name Identifying components and their use 1.1.10 Keyboard The keyboard Keyboai
is the main device for A computers. used to text or enter commands into the PC. Nowadays keyboards with additional features are available like multimedia keyboard, wireless keyboard. Mouse input