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Introduction to Computers. Prof. Sokol Computer and Information Science Brooklyn College. What is a Computer?. A COMPUTER is an electronic device that can: Receive information Perform processes Produce output Store info for future use. Information Processing Cycle. Input Process

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Introduction to computers

Introduction to Computers

Prof. Sokol

Computer and Information Science

Brooklyn College

What is a computer
What is a Computer?

A COMPUTER is an electronic device that can:

  • Receive information

  • Perform processes

  • Produce output

  • Store info for future use.

Information processing cycle
Information Processing Cycle

  • Input

  • Process

  • Output

  • Storage

Hardware vs. Software

  • Hardware - the physical parts that make up the computer

    • e.g. CPU, memory, disks, CD-ROM drives, printer.

  • Software - computer programs and applications.

    • Operating system, word processor, games, etc.

Hardware physical devices that comprise a computer system
Hardware: physical devices that comprise a computer system

Monitor (output)

Speaker (output)

System unit

(processor, memory…)

Printer (output)

Storage devices

(CD-RW, Floppy, Hard disk, zip,…)

Mouse (input)

Scanner (input)

Keyboard (input)

What are the primary components of a computer
What Are The Primary Components Of A Computer ?

  • Input devices.

  • Central Processing Unit (control unit and arithmetic/logic unit).

  • Memory.

  • Output devices.

  • Storage devices.

Input devices
Input Devices

  • Keyboard

  • Mouse

  • Scanner

  • Camera

  • Microphone

  • Touchpad

  • Stylus

  • …..

Central processing unit

Central Processing Unit

The central processing unit (CPU) is the “brain” of the computer. It:

interprets instructions to the computer (control unit),

performs the arithmetic and logical processing (ALU)

Cpu s

  • CPU’s are measured by their (clock) speeds, or frequency of instructions per second. Example: 2.4 GHz

  • A multi-core processor has several processing units and can do more than one thing at a time. Example: duo or quad core.



Memory, also called Random Access Memory or RAM stores:

instructions waiting to be executed

data needed by those instructions

results of processed data

Any information stored in RAM is lost when the computer is turned off.


  • Data in memory is stored as binary digits (BITS) e.g. 011100101010

  • 1 BYTE = 8 bits

  • 1 byte usually stores 1 text character.

Amount of ram in computers

Amount Of RAM In Computers

We measure the size of memory by telling how many bytes it can hold.

1 kilobyte = 210 bytes = 1024 bytes

1 megabyte = 220 bytes = ~1 million bytes

1 gigabyte = 230 bytes = ~1 billion bytes

1 terabyte = 240 bytes = ~1 trillion bytes

Typical RAM size: 2 to 4 GB.

Note: a 32 bit OS can only handle up to 4GB of RAM since 232=4GB.

Output devices

Output Devices

Output devices make the information resulting from the processing available for use.

printer - produces a hard copy of your output

screen - produces a soft copy of your output

speakers, etc.

Storage devices

Storage Devices

Auxiliary storage devices are used for permanent storage of data.

magnetic disks (hard disks, floppy disks)

optical disks (CD and DVD drives)

USB drives and flash memory cards

Hard disks magnetic storage
Hard Disks (magnetic storage)

  • Permanent storage that is inside of the computer, and NOTportable.

  • Consists of several platters which spin very fast

  • Typical hard disks range from 80 GB to 2 Terabytes

Optical discs
Optical Discs

Use laser to read and write:

  • CD-ROM (read only memory),

  • CD-RW – (rewritable)


  • DVD+RW

    Typical CD’s can store about 700 MB

    Typical DVD’s can store up to 17 GB

Flash memory
Flash Memory


  • Small, easy to carry around

  • High memory capacity – up to 256 GB


    There are several different forms of flash memory, for e.g. USB drives, CompactFlash, Secure Digital, xD Picture Card.


  • A computer program or software tells it exactly what to do.

  • A computer program is a set of instructions to the computer.

  • The computer does one instruction at a time. (Note: each core performs one instruction at a time.)



Computer software is the key to productive use of computers. Software can be categorized into two types:

System software

Application software.

System software

System Software

The most important system software is the operating system.

Examples of operating systems:

Windows, DOS, Apple, UNIX, Linux

What is an operating system
What is an operating system?

An OS is a computer program that:

  • Controls the hardware of the computer,

  • Enables you to communicate with the computer.

Application software

Application Software

Application Software consists of programs that tell a computer how to produce information. Some of the more commonly used packages are:

Word processing

Electronic spreadsheet


Presentation graphics

Word processing
Word Processing

  • Word Processing software is used to create and print documents. A key advantage of word processing software is that users easily can make changes in documents.

Electronic spreadsheets
Electronic Spreadsheets

  • Electronic spreadsheet software allows the user to add, subtract, and perform user-defined calculations on rows and columns of numbers. These numbers can be changed and the spreadsheet quickly recalculates the new results.

Database software
Database Software

Allows the user to enter, retrieve, and update data in an organized and efficient manner, with flexible inquiry and reporting capabilities.

Presentation graphics
Presentation Graphics

  • Presentation graphic software allows the user to create documents called slides to be used in making the presentations. Using special projection devices, the slides display as they appear on the computer screen.