The Computer Defined
 A computer is an electronic device that processes data,
converting it into information that is useful to people.
Analog and Digital Computer
 Analog systems represent data as variable points along
a continuous spectrum of values.
 Early analog computers were mechanically devices,
weighing several tons and using motors and gears to
perform calculations.
 Digital systems represents data as having one distinct
value or another with no other possibilities.
 Digital computers are so called because they work by
the numbers.That is they break all types of
information into tiny units and use numbers to
represent those pieces of information.
Computers for individual users
 Most computers are meant to be used by only one
person at a time.Such computers are shared by several
people,but only one user can work with the machine at
any given moment.
Six primary types of computers
 Desktop computers
 Workstations
 Notebook computers
 Tablet computers
 Handheld computers
 Smart phones
These systems are all examples of Personal Computers
Personal computers are also called micro computers
Desktop Computers
 The most common type of personal computer is the
desktop computer…………….a PC that is designed to sit
on a desk or table.
 These computers you see in schools ,homes, offices.
 These computers are used to communicate, produce
music, edit photographs and videos, play sophisticated
games and much more.
Workstations
 A workstation is a speacialized,single user computer
that typically has more power and features than a
standard desktop personal computer.
 These machines are popular among scientists,engineer
who need a system with grater than average speed and
the power to perform sophisticated tasks.
 Workstations often have large high resolutions
monitors and accelerated graphics handling
capabilities.
Notebook Computer
 Notebook computers as their name implies
approximate the shape of an 8.5 by 11 inch notebook
and easily fit inside a briefcase.
 People frequently use these devices on their lap they are
also called laptop computers.
Tablet PCs
 The tablet PC is the newest development in portable ,
full featured computers.
 Tablet PCs offer all the functionality of a notebook PC
 They are lighter and can accept input from a special
pen called a stylus or a digital pen.
Handheld PCs
 Handheld personal computers are computing devices
small enough to fit in your hands.
 Personal digital assistant (PDA) is the type of
handheld computers.
 Size of PDA is no larger than small appointment book
and is normally used for special applications
 Displaying telephone numbers and addresses
 Taking notes
 Keeping track of dates or agendas
Smart phones
 Some cellular phones double as miniature PCs
 These phones offer advanced features ,that’s way they
are called smart phones
 These features can include
 Web service
 E-mail services
 Special software such as personal organizers
 Special hardware such as digital cameras or music
players etc.
Computer for Organizations
 Some computers handle the need of many users at the
same time.
 The largest organizational computers support
thousands of individual users at the same time, from
thousands of miles away.
Network servers
 Today,most organization’s network are based on
personal computer
 Individual users have their own desktop computers
which are connected to one or more centralized
computers,called network servers.
 Large organizations may have dozens or hundreds of
individual servers working together at the heart of
their network
 When set up in such groups sometimes called clusters
or server farms
 In these large networks different group of servers may
have different purposes
 Handling printing tasks
 Enabling internet communications
 Accounting tasks
 Word processing
 Database management tasks
Mainframe computres
 Mainframe computers are used in large organizations
such as insurance companies and banks, where many
people frequently need to use the same data.
 In a traditional mainframe environment,each user
access the mainframe’s resources through a device
called a terminal
Types of terminal
 A dumb terminal
 An intelligent terminal
A dumb terminal
 A dumb terminal does not process or store data
 It is simply an input/output device that function as a
window into a computer located somewhere else.
An intelligent terminal
 An intelligent terminal can perform some processing
operations but it usually does not have any storage.
The Parts of a Computer System
 A complete computer system consists of four parts
 Hardware
 Software
 Data
 User
Hardware
 The mechanical devices that make up the computer
are called hardware
 Hardware is any part of the computer you touch
Software
 Software is a set of instructions that makes the
computer perform tasks
 The term program refers to any piece of software.
Data
 Data consists of individual facts or pieces of
information that by themselves may not make much
sense to a person.
 Tiny pieces of data in various form is actually the
useful information.
Users
 People are the computer operators, also known as
users
 No computer is totally autonomous
The information processing cycle
 A computer converts data into information by
performing various action.
 During performing a mathematical operation on two
numbers,then display the result.This is called the
information processing cycle.
 The information processing cycle has four parts
 Input
 Processing
 Output
 storage
Essential Computer hardware
 A computer’s hardware devices fall into one of four
categories
Processor
2. Memory
3. Input and Output
4. Storage
1.
Processing devices
 The processor is like the brain of the computer
 It organizes and carries out instructions that come
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from either the user or software.
Processor usually consists of one or more speacialized
chips called microprocessors.
Microprocessor is plugged into the computer’s
motherboard
Motherboard is an example of circuit board
Many internal devices like sound card,video card,disk
controller are attached to the mother board.
Memory devices
 In a computer, memory is one or more sets of chips
that store data and program instructions either
temporarily or permanently.
Random Access Memory
 The most common type of memory is called random access
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memory(RAM)
RAM is like an electronic scratch pad inside the computer.
RAM holds data and program instructions while the CPU
works with them.
When a program is launched it is loaded into and run from
memory
RAM is also called read/write memory
RAM is made up of a set of chips mounted on a small
circuit board.
RAM is also volatile ,meaning that it lost its contents when
computer is shut off.
Read Only Memory
 Unlike RAM ,read only memory (ROM) permanently
stores its data, even when the computer is off.
 RAM is called non volatile memory because it never
lost its contents
 ROM holds instructions that the computer needs to
operate.
Input and Output devices
 Input devices accept data and instructions from the
user or from another computer
 Out put devices return processed data to the user or to
another system.
 The most common input device is the keyboard,which
accept letters,numbers and commands from the user.
 Another type is mouse
Examples of input devices
 The trackball and touchpad
 The joystick
 A scanner
 A digital Camera
 A microphone
 The function of an output device is to present
processed data to the user
 The most common output devices are monitor and the
printer
Storage Devices
 The purpose of storage is to hold data permanently
,even when the computer is turned off.
 Storage as an electronic file cabinet and RAM as an
electronic worktable.
 When you work with a program or set of data,the
computer locates it in the file cabinet and puts a copy
on the table.
What is storage and memory
 There are three major distinctions between storage
and memory
 There is more room in storage than in memory
 Contents are retained in storage but not in memory
 Storage devices operate much slower than memory
chips
Two types of storage
 Magnetic storage
 Optical storage
Magnetic storage
 There are many types of computer storage but the
most common is magnetic disk.
 A disk is round, flat object that spins around its center.
Optical storage
 Every computer sold today includes at least one form
of optical storage
 Devices that use lasers to read data from or write data
to the reflective surface of an optical disc
 The CD-ROM DRIVE is the most common type of
optical storage device
 An increasingly popular data storage technology is the
digital video disc (DVD)
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