Download What is a Computer?

What is a Computer?
A computer is an electronic device
operating under the control of
instructions stored in its own
memory unit, that can accept data
(input) process the data and
generate results (output) and
store the results for future use.
Hardware & Peripheral devices
• The electric, electronic, and mechanical
equipment that makes up a personal
computer is called hardware.
• Devices that surround the system unit (i.e.,
the keyboard, mouse, speakers, monitor,
and so on) sometimes are known as
peripheral devices.
• other devices (such as a scanner) that
could be part of a computer system.
Information Processing Cycle
• Four general operations of computer
•
Input
•
Process
•
Output
•
Storage
Data Vs Information
• Data is a collection of raw facts, figures,
and symbols, such as numbers, words,
images, video and sounds
• Data is given to computer during the input
operation
• Computers manipulate the data and
produce organized, meaningful and useful
information
Processing speed
• Today’s supercomputer can perform 1.8
trillion operations per second.
• If a person did one arithmetic operation a
second without stopping, it would take
more than 31,000 years to perform the
number of operations a supercomputer
can do in one second.
Computer users, end users or just
users
• People who use the computer directly or
use the information it generates are called
computer users, end users, or sometimes,
just users.
Why is a computer so Powerful?
• The power of a computer comes from its
ability to perform the information
processing cycle quickly, reliably (low
failure rate), and accurately.
• capacity to store large amounts of
information
• ability to communicate with other
computers
Computer Program or Software
• A detailed set of instructions that tells
computer exactly what to do to perform an
operations are called a computer program
or software.
What is the difference between hardware
and software?
Hardware Vs Software
• A 3.5 inch floppy disk is a hardware but
the program that is stored in a floppy disk
is a software
• Computer programs are written using
programming languages (such as BASIC,
COBOL, C, Pascal, and so on) each of
which has specific rules, or syntax,
governing its use.
Components of a computer
• Six primary components of the computer are
–
–
–
–
–
–
Input devices
Processor (control unit and arithmetic/logic unit)
Memory
Output devices
Storage devices
Communication devices
The processor, memory, and storage devices are
inside the system unit.
Input Devices
• An input device is an hardware component
that allows you to enter data, programs,
commands and so on in to a computer
• Different types of input devices are
designed to transmit different types of data
or to transmit data in different ways.
• The two primary input devices used are
the keyboard and the mouse
Keyboard
• Keyboard contains keys you press to enter
data into the computer
• A desktop computer keyboard typically has
101 to 105 keys
Mouse
• The mouse is called a pointing device
because it controls the movement of a
pointer, or mouse pointer, on the computer
screen and make selections from the
screen.
• The mouse either use optical sensor or
ball that detects the movement of the
mouse
Processor
• Also called Central Processing Unit
• It has two units: Control Unit and
Arithmetic logic unit.
• The control unit interprets the instructions
• The arithmetic logic unit (ALU) performs
logical and arithmetic operations.
• Example: Celeron, Athlon XP, Pentium
processors
Memory
• Also known as RAM (Random Access
Memory)
• It stores
– Instructions
– Data
– Results (information)
• Amount of memory in computers typically
is measured in kilobytes or megabytes
Output Devices
• Display the processed information
• Example: Printer, Display device
• Two types of printer
– Impact
– Nonimpact
Impact and non impact printer
• Impact printer prints by striking an inked
ribbon against the paper
– Dot matrix printer
• Non impact printers form characters by
means other than striking a ribbon against
paper
– Laser printers
– Ink-jet printers
Advantages of Non impact printers
• It can print higher quality text and graphics
than an impact printer
• It also do better job printing different fonts
Display Devices
• A monitor is a display device that display the processed
output.
• Two basic types of monitor
– CRT (cathode ray tube)
– LCD (liquid crystal display)
• CRT is the most common display device used with
desktop computers
• LCD also called flat panel monitor uses a liquid display
crystal, similar to digital watch, to produce images on the
screen
• Monitor is composed of individual picture elements
called pixels
Byte or Memory location
• 1 byte = 8 bits
• 1KB = about 1,000 bytes, (1024 or 2^10)
• 1MB = about 1,000,000 (one million)
bytes, (1,048,576 or 2^20)
• 1GB= about 1,000,000,000 (one billion)
bytes (1,073,741,824 or 2^30)
Storage Devices
• Storage devices are used to store instructions,
data, and information when they are not being
used in memory
• Six common types of storage devices are
–
–
–
–
–
–
floppy disks
zip disks
hard disk
optical discs
tape
Miniature storage media
Floppy Disks
• Floppy disk is a portable storage medium
• It consists of a thin, circular, flexible plastic disk
with a magnetic coating enclosed in a squareshaped plastic shell
• A floppy disk drive is a device that can read from
and write to a floppy disk
• Formatting is the process of preparing a disk for
reading and writing by organizing the disk into
storage locations called track and sectors
Zip Disks
• Portable magnetic media
• Hold about 500 times more than a
standard floppy disk
• Used to back up important data and
information
Hard Disk
• A hard disk consists of one or more rigid
metal platters coated with a metal oxide
material that allows data to be recorded
magnetically
• personal computer hard disks usually are
fixed (i.e., not removable),
• some portable computers have removable
hard disk drives
Optical disc
• Uses laser technology for recording
• Two types of optical discs are CD
(compact disc) and DVD (digital video
disc)
• CDs are available in a variety of formats
– CD-ROM
– CD-R
– CD-RW
Optical disc
• DVDs are available in the following
formats
– DVD-ROM
– DVD-RW
TAPE
• Capable of storing large amounts of data
and information at a low cost
• Primarily used for long-term storage and
backup
Miniature Storage Media
• Rewritable media usually in the form of a
flash memory card
• It is the primary storage media used with
digital cameras, music players, PDAs and
so on
Communication Devices
• Helps a computer to send and receive
data, instructions, and information to and
from one or more computers
• Communication occur over transmission
media, such as cables, telephone lines,
satellites
Computer software
• Can be categorized in to two types
– System software
– Application software
• System software is a program that controls the
operations of computer equipment
• Operating system is a part of system software
• Application software consists of program that tell
a computer how to produce information
– Example: Word Processing, Spredsheet, database,
presentation graphics
Networks
• A network is a collection of computers and
devices connected through the
communication media such as cables,
telephone lines, modems or other means
– Local area network
– Wide area network
Internet & Intranets
• Worlds largest network
• Links millions of computers by means of cables,
telephone lines and other communication
devices
• Users connect to the Internet either through an
internet service provider or through an online
service provider
• Intranet is a special type of web that is available
only to the users of a particular type of computer
network, such as a network used within a
company or organization for internal
communication.
World Wide Web
• Contains billions of document called web pages
• Web site is a collection of web pages
• Web browser helps to access and view web
pages
• Each web page has a unique address called
URL (Uniform Resource Locator)
• URL consists of a protocol, domain name, and
sometimes the path to a specific web page.
• Web server is a computer that delivers
requested web pages
World Wide Web
• The first web page in the web site is called
the home page
• A hyperlink is colored or underlined text or
a graphic that, when clicked, connects to
another web page
• Microsoft Internet Explorer is a widely
used browser
Electronic Commerce
• Conducting business activities online
• Three types of e- commerce
– Business to Consumer (B2C) Business selling
goods/products to the general public
– Consumer to Consumer (C2C) Consumer
selling directly to another consumer
– Business to Business (B2B) Business
provides goods and services to other
businesses