Posted by: wasaa | June 22, 2008

Input Devices



Peripheral devices that are used to enter commands or information into a computer, such as the keyboard, mouse, joystick, modem, scanner, and touch screen


Key Board

Joy Stick

Digital Camera

Track ball

Wireless optical mouse

Touch pad

Track stick

Bar code reader




Punch card

Web Camera

Light pen

Touch Screen

Data Glove (The Data-Glove is the device that most people think of when talking about VR input devices. It is the device that allows us to do everything in the virtual world that our real hand can do in the real world. The data glove is the translator from real to virtual.)


Output Devices

CRT Monitor

Laser Printer

Dot matrix Printer

Inkjet Printer




Internal storage areas in the computer. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk. Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.


There are several different types of memory:


         RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost.

         ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to.

         PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.

         EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light.

         EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge

Magnetic Tape (Mass storage for Backup)

Flash drive / Thumb drive(Removable)

Hard Disk Drive

51/2 Floppy disk

Zip Disk 1.44 100MB

31/2 Floppy disk 1.44 MB

         CD 640/700MB (CD- ROM = Compact Disc Read Only Memory

         CD-R = Compact Disc Recordable (Once)

         CD-RW= Compact Disc Rewritable (Many time)

Types of DVDs

(Digital Versatile Disc)

Single Side Single layer = 4.5GB

Double Side Single layer = 9.4GB

Single Side Double layer = 8.54GB

Double Side Double layer = 17GB

DVD-R/RW Formats
Five types of recordable DVD products currently exist on the market. Some are approved and supported by the DVD Forum and some are not.Industry standard and recognized by the DVD Forum:
  DVD-R = DVD Recordable
  DVD-RW = DVD Rewritable



  DVD-RAM = DVD Random Access MemoryThe main features of the DVD formats can be summarized as follows:

        Backwards compatibility with current CD media (at least the newest models of DVD drives)

        Physical dimensions identical to compact disc with total thickness equal to 1.2 mm, but with capacity at least 7 times larger than that of CD.

        Capacities of 4.7 GB, 8.54 GB, 9.4 GB, and 17.08 GB, depending on the disk structure.

        Single-layer/dual-layer and single/double sided options.

        DVD replication process is similar to that used for compact disks.

        A disc-based format means fast random access like in hard drives and CDs and unlike tapes.

        Designed from the outset for video, audio and multimedia. Meets the requirement for 133 minutes of high quality video on one side of a disk.

        DVD-ROM for enhanced multimedia and games applications.

        DVD-Video for full length high quality movies on one disc.

        DVD-Audio for higher quality music, surround sound and optional video, graphics and other features.

        All formats use a common file system.

        Copy protection built into standard (unless it is broken…)



A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.


Central Processing Unit (CPU)

The central processing unit performs the majority of calculations and controls the operation of a computer. CPUs are rated by the speed at which they can execute instructions.  The speed of a CPU is measured in Megahertz (MHz), and is also known as the clock speed. The higher the value of the speed the faster the computer can run programs. The capacity of a CPU is expressed in terms of word size. A word is the maximum number of bits that the CPU can manipulate or store at one time




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