Seema Sirpal Delhi University Computer Centre
What is a Computer?
An electronic device that stores, retrieves, and processes data, and can be programmed with instructions. A computer is composed of hardware and software, and can exist in a variety of sizes and configurations.
Hardware & Software
The term hardware refers to the physical components of your computer such as the system unit, mouse, keyboard, monitor etc.
The software is the instructions that makes the computer work. Software is held either on your computers hard disk, CD-ROM, DVD or on a diskette (floppy disk) and is loaded (i.e. copied) from the disk into the computers RAM (Random Access Memory), as and when required.
Types of Computers
Mini and Mainframe Computers Very powerful, used by large organisations such an banks to control the entire business operation. Very expensive! Personal Computers Cheap and easy to use. Often used as stand-alone computers or in a network. May be connected to large mainframe computers within big companies.
Input Devices -- "How to tell it what to do“ - A keyboard and mouse are the standard way to interact with the computer. Other devices include joysticks and game pads used primarily for games. Output Devices -- "How it shows you what it is doing" - The monitor (the screen) is how the computer sends information back to you. A printer is also an output device.
INPUT DEVICES The Mouse Used to ‘drive’ Microsoft Windows The Keyboard The keyboard is still the commonest way of entering information into a computer Tracker Balls an alternative to the traditional mouse and often used by graphic designers
INPUT DEVICES Scanners A scanner allows you to scan printed material and convert it into a file format that may be used within the PC Touch Pads A device that lays on the desktop and responds to pressure Light Pens Used to allow users to point to areas on a screen Joysticks Many games require a joystick for the proper playing of the game
OUTPUT DEVICES VDU The computer screen is used for outputting information in an understandable format Printers There are many different types of printers. In large organizations laser printers are most commonly used due to the fact that they can print very fast and give a very high quality output.
OUTPUT DEVICES Plotters A plotter is an output device similar to a printer, but normally allows you to print larger images. Speakers Enhances the value of educational and presentation products. Speech synthesisers Gives you the ability to not only to display text on a monitor but also to read the text to you
Storage Devices -- "How it saves data and programs“ - Hard disk drives are an internal, higher capacity drive which also stores the operating system which runs when you power on the computer. - "Floppy" disk drives allow you to save work on small disks and take the data with you.
Speed: Very fast! The speed of a hard disk is often quoted as "average access time" speed, measured in milliseconds. The smaller this number the faster the disk. Capacity: Enormous! Often 40/80 Gigabytes. A Gigabyte is equivalent to 1024 Megabytes. Cost: Hard disks costs are falling rapidly and normally represent the cheapest way of storing data.
Diskettes (Floppy Disks) Speed: Very slow! Capacity: Normally 1.44 Mbytes. Cost: Very cheap.
CD-ROM Disks Speed: Much slower than hard disks. The original CD-ROM speciation is given a value of 1x speed, and later, faster CD-ROMs are quoted as a multiple of this value. Capacity: Around 650 Mbytes and more
DVD Drives Speed: Much faster than CD-ROM drives but not as fast as hard disks. Capacity: Up to 17 Gbytes. Cost: Slightly higher than CD-ROM drives.
Main Parts of Computer
Memory -- "How...
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