Introduction to Computers - Introduction to Computer Science - Lecture Slides, Slides of Computer Science

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Introduction to Computers

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What Is A Computer?

A computer is an electronic device, operating under the control of instructions (software) stored in its own memory unit, that can accept data (input), manipulate data (process), and produce information (output) from the processing. Generally, the term is used to describe a collection of devices that function together as a system.

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What Does A Computer Do?

Computers can perform four general operations, which comprise the information processing cycle.

 Input

 Process

 Output

 Storage

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Data and Information

 All computer processing requires data , which is a collection of raw facts, figures and symbols, such as numbers, words, images, video and sound, given to the computer during the input phase.  Computers manipulate data to create information. Information is data that is organized, meaningful, and useful.  During the output Phase, the information that has been created is put into some form, such as a printed report.  The information can also be put in computer storage for future use.

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How Does a Computer Know

what to do?

 It must be given a detailed list of instructions,

called a compute program or software ,

that tells it exactly what to do.

 Before processing a specific job, the

computer program corresponding to that job

must be stored in memory.

 Once the program is stored in memory the

compute can start the operation by executing

the program instructions one after the other.

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What Are The Primary

Components Of A Computer?

 Input devices.

 Central Processing Unit (containing the control unit and the arithmetic/logic unit).

 Memory.

 Output devices.

 Storage devices.

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The Keyboard

The most commonly used input device is the keyboard on which data is entered by manually keying in or typing certain keys. A keyboard typically has 101 or 105 keys.

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The Mouse

Is a pointing device which is used to control the movement of a mouse pointer on the screen to make selections from the screen. A mouse has one to five buttons. The bottom of the mouse is flat and contains a mechanism that detects movement of the mouse.

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Memory

Memory also called Random Access Memory or RAM (temporary memory) is the main memory of the computer. It consists of electronic components that store data including numbers, letters of the alphabet, graphics and sound. Any information stored in RAM is lost when the computer is turned off.

Read Only Memory or ROM is memory that is etched on a chip that has start-up directions for your computer. It is permanent memory.

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Amount Of RAM In Computers

The amount of memory in computers is typically measured in kilobytes or megabytes. One kilobyte (K or KB) equals approximately 1,000 memory locations and one megabyte (M or MB) equals approximately one million locations A memory location, or byte, usually stores one character. Therefore, a computer with 8 MB of memory can store approximately 8 million characters. One megabyte can hold approximately 500 pages of text information.

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Storage Devices

Auxiliary storage devices are used to store data when they are not being used in memory. The most common types of auxiliary storage used on personal computers are floppy disks, hard disks and CD-ROM drives.

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Floppy Disks

A floppy disk is a portable, inexpensive storage medium that consists of a thin, circular, flexible plastic disk with a magnetic coating enclosed in a square-shaped plastic shell.

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 The disk’s storage locations are divided into pie- shaped sections called sectors.

 A sectors is capable of holding 512 bytes of data.

 A typical floppy stores data on both sides and has 80 tracks on each side with 18 sectors per track.

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Hard Disks

 Another form of auxiliary storage is a hard disk. A hard disk consists of one or more rigid metal plates coated with a metal oxide material that allows data to be magnetically recorded on the surface of the platters.

 The hard disk platters spin at a high rate of speed, typically 5400 to 7200 revolutions per minute (RPM).

 Storage capacites of hard disks for personal computers range from 10 GB to 120 GB (one billion bytes are called a gigabyte).