Overview3x

addictedswimmingΤεχνίτη Νοημοσύνη και Ρομποτική

24 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

49 εμφανίσεις

HARDWARE COMPONENTS

The

computer

is

a

system

in

which

programs

(software)

can

execute

with

appropriate

input

data

and

produce

desired

results
.


The central processing unit (CPU)



Main memory, also known as random
access memory (RAM)



The storage devices



The main input/output (I/O) devices



Communication ports

EVOLUTIONARY HISTORY OF MODERN
COMPUTER

First Generation
-

1940
-
1956: Vacuum Tubes


The first computers used vacuum tubes for circuitry and
magnetic drums

for
memory
, and were often enormous, taking
up entire rooms.


First generation computers relied on
machine language
.


The UNIVAC and
ENIAC

computers are examples of first
-
generation computing devices.

Second Generation
-

1956
-
1963: Transistors


Transistors

replaced vacuum tubes and ushered in the second
generation of computers.


These computers were smaller, faster, cheaper, more energy
-
efficient
and more reliable


Second
-
generation computers still relied on punched cards for input
and printouts for output.



These computers moved from cryptic
binary

machine language to
symbolic, or
assembly
, languages.



Third Generation
-

1964
-
1971:
Integrated Circuits


The development of the
integrated circuit

was the
hallmark of the third generation of computers.


Transistors were miniaturized and placed on
silicon

chips
, called
semiconductors
.

Computer processing speed drastically increased.


keyboards

and
monitors

were introduced in this generation.


Computers for the first time became accessible to a mass audience because they
were smaller and cheaper.

Fourth Generation
-

1971
-
Present: Microprocessors


thousands of integrated circuits were built onto a single silicon chip.


The Intel 4004 chip, located all the components of the computer
-

from the
central
processing unit

and memory to input/output controls
-

on a single chip.


As these small computers became more powerful, they could be linked together to
form networks.

Fifth Generation
-

Present and
Beyond: Artificial Intelligence


Fifth generation computing devices, based on
artificial intelligence


As a part of fifth generation feature
voice
recognition

can be taken, that are being used today.


Quantum computation

and molecular and
nanotechnology

will radically change the face of
computers in years to come.


The goal of fifth
-
generation computing is to develop
devices that respond to
natural language

input and
are capable of learning and self
-
organization.



INPUT DEVICE:
-

Any machine that feeds
data

into a
computer
.


For example, a
keyboard

is an input device. Other
input devices are
Mouse
,
trackballs

etc.



OUTPUT DEVICE:
-

Whereas a
display monitor

is an
output device
.
Printer is another example of output device.

INPUT
DEVICES

KEYBOARD

MOUSE

SCANNER

TRACKBALL

JOYSTICK

Keyboards:

the most
frequently used input
devices, are used to enter
instructions and data via
keys.

There are many variations on
the layout and labeling of
keys.

Extra numeric keys may be
added, as may special
-
purpose

function keys, whose effects
can be defined by programs
in the computer.

Scanners:

produce a digital
image of a document for
input and storage in a
computer, using
technology similar to that
of a photocopier.


Small scanners can be
passed over the document
surface by hand; larger
versions have a flat bed,
like that of a photocopier,
on which the input
document is placed and
scanned.








MOUSE (Manually Operated
Utility Service Equipment):

A
device

that controls the movement of
the
cursor

or
pointer

on a
display
screen
.



A mouse is a small
object

the user
can roll along a hard, flat surface.



Its name is derived from its shape,
which looks a bit like a mouse, its
connecting wire that one can
imagine to be the mouse's tail, and
the fact that one must make it move
along a surface.




As the user moves the mouse, the
pointer on the display screen moves
in the same direction.

TRACKBALL:


A
trackball

is a
pointing device

consisting of a
ball

held by a
socket containing sensors to
detect a rotation of the ball
about two axes

like an upside
-
down
mouse

with an exposed
protruding ball.


The user rolls the ball with the
thumb
,
fingers
, or the palm of
the
hand

to move a
cursor
.

JOYSTICK:


A
joystick

is an input device consisting of a
stick that pivots on a base and reports its angle or
direction to the device it is controlling.


Joysticks are often used to control video games,
and usually have one or more push
-
buttons
whose state can also be read by the computer.


A popular variation of the joystick used on
modern
video game consoles

is the
analog stick
.


OUTPUT
DEVICES

MONITOR

PRINTER


MONITOR: Another term for
display
screen
. The term
monitor,

however,
usually refers to the entire box, whereas
display screen can mean just the screen.
In addition, the term
monitor

often
implies
graphics

capabilities




There are many ways to classify
monitors. The most basic is in terms of
color capabilities, which separates
monitors into three classes:


monochrome

: Monochrome monitors
actually display two colors, one for the
background

and one for the
foreground
.
The colors can be black and white, green
and black, or amber and black.


gray
-
scale

: A gray
-
scale monitor is a special
type of monochrome monitor capable of
displaying different shades of gray.


Color monitors

can display anywhere from
16 to over 1 million different colors. Color
monitors are sometimes called
RGB
monitors

because they accept three
separate signals
--

red, green, and blue.


PRINTER
:

A
device

that prints
text

or illustrations on paper. There are many
different types of printers. In terms of
the technology utilized, printers fall into
the following categories:


DAISY WHEEL


DOT MATRIX


INK JET


LASER


LCD LED


LINE PRINTER


THERMAL PRINTER

INTEGRATED INPUT OUTPUT DEVICE

LAPTOP:


A laptop is a
personal computer

designed for
mobile use
.


A laptop integrates most of the
typical components

of a
desktop
computer
.


They usually have a touch screen
display and some include
handwriting recognition or graphics
drawing capability.


RAM



A type of
computer memory

that can
be
accessed

randomly.



RAM is the most common type of
memory found in
computers



There are two basic types of RAM:


dynamic RAM (DRAM)


static RAM (SRAM)



.

ROM


is a class of
storage

media used
in
computers

and other
electronic devices.




Because data stored in ROM
cannot be modified, it is mainly
used to distribute
firmware
.



Modern
semiconductor

ROM
chips

are not immediately
distinguishable from similar
chips like
RAM

modules,
except by the part numbers
printed on the
package
.


Hard disk:


Hard Disk drives (HDDs) for
PCs

generally have
seek
times

of about 12
milliseconds

or less.




Many disk drives improve
their performance through a
technique called
caching
.



it’s a sort of secondary
memory where data can be
stored permanently.

CPU
:
-

central processing unit
, is the
brains of the
computer
.


Sometimes referred to simply as the
processor

or
central processor,





In terms of computing power, the CPU
is the most important element of a
computer system
.



Two typical components of a CPU are:



The
arithmetic logic unit

(ALU)
, which
performs arithmetic and logical
operations.



The
control unit

(CU)
, which extracts
instructions

from
memory

and decodes
and
executes

them, calling on the ALU
when necessary.



USE OF COMPUTER NETWORKS



NETWORKS FOR COMPANIES


RESOURCE SHARING (e
-
commerce)


HIGH RELIABILITY (backup facility)


SAVING MONEY (sending information, online shopping)


COMMUNICATION MEDIUM (EDI, EFT)


NETWORK FOR PEOPLE


ACCESS TO REMOTE INFORMATION (browsing sites)


INTERACTIVE ELECTRONIC ENTERTAINMENT (online
movie)


PERSON TO PERSON COMMUNICATION (e
-
mail,
chatting, video conferencing)



DEFINITION OF COMPUTER NETWORKS

CLIENT MACHINE

SERVER MACHINE

SERVER PROCESS

CLIENT

PROCESS

REQUEST

REPLY

NETWORK

Definition:
-

the merging of computers and communications has had a profound
influence on the way computer systems are organized. The concept of the
“computer center” as a room with a large computer to which users bring their
work for processing is now totally obsolete. The old model of a single computer
serving all of the organization’s computational needs has been replaced by one in
which a large number of separate but interconnected computers do the job. These
systems are called computer networks
.

NETWORK HARDWARE


BROADCAST NETWORK :
this has a single
communication channel that is shared by all the machines on
the

network. Short messages called packets in certain
contexts, sent by any machines are received by all the others.


POINT
-
TO
-
POINT:

It consists of many connections between
individual pairs of machines. To go from the source to destination, a
packet on this type of network may have to visit one or more
intermediate machines.

BROADCASTING

POINT
-
TO
-
POINT

NETWORK HARDWARE

CLASSIFICATION OF INTERCONNECTED
PROCESSORS BY SCALE

INTERPROCESSOR
DISTANCE

PROCESSORS
LOCATED IN SAME

EXAMPLES

0.1M

CIRCUIT BOARD

DATA FLOW MACHINE

1 M

SYSTEM

MULTICOMPUTER

10 M

ROOM

LAN

100 M

BUOLDING

LAN

1 KM

CAMPUS

LAN

10 KM

CITY

MAN

100 KM

COUNTRY

WAN

1,000 KM

CONTINENT

WAN

0,000 KM

PLANET

THE INTERNET


STAR NETWORK


RING NETWORK


BUS NETWORK

Bus Network with Backbone

Token Ring Network Topology

Self
-
healing Ring Topology

Two rings


Star Network Topology

Network Topology


LAN


MAN


WAN


WIRELESS NETWORKS


INTERNETWORKS

LAN (LOCAL AREA NETWORK)



These are privately
-
owned networks within a single building or campus of
upto a few kilometers in size.


They are widely used to connect personal computers and workstations In
company offices and factories to share resources (printer) and exchange
information.


Their size is small than other network.


Their transmission technology is developed than other networks.


They differ in the topology from other networks.


Bus topology

Ring topology


cable


computer

TOKEN RING
TRANSMISSION


It is basically the bigger version of LAN and normally uses similar
technology.


It may cover a group of nearby corporate offices or a city.


It might be public or public.


It can support both data and voice.

MAN(METROPOLITAN AREA
NETWORK)

3

1

2

N

computer

Bus A

Head end

Direction of flow on bus A

Direction of flow on bus B


It spans a large geographical area.


It contains a collection of machines intended for running user programs.


The hosts (end systems) are connected by communication subnet.


The job of subnet is to carry messages from host to host.


In WAN we find circuits and switching elements.


The switching computers are generally called routers.


WAN (WIDE AREA NETWORK)

host

router

subnet

LAN

RELATION BETWEEN HOSTS AND THE SUBNET


Mobile networks, such as notebook computers and personal digital assistants
(PDAs) and the fastest
-
growing segment of the computer industry.

WIRELESS NETWORK

Wireless

Mobile

applications

NO

NO

Stationary workstations in
offices

NO

YES

Using a portable in a hotel;
train maintenance

YES

NO

LANs in older, unwired
buildings

YES

YES

Portable office; PDA for store
inventory



Many networks exist in the world, often with
different hardware and software. People
connected to one network often want to
communicate with people attached to a different
one. This desire requires connecting together
different, and frequently incompatible networks,
sometimes by using machines called gateways
to make the connections and provide the
necessary translation, both in terms of hardware
and software. A collection of interconnected
networks is called an internetwork or simply
internet.

INTERNET

Internet



To reduce their design complexity, most networks are organized as a series of Layers or levels,
each one built upon the one below it.


The number of layers, the name of each layer, and the function of each layer differ from
network to network.


Layer
n

on one machine carries on a conversation with layer
n

on another machine.


The rules and conventions used in this conversation are collectively known as the
layer n
protocol.


A protocol is an agreement between the communicating parties on how communication is to
proceed.


The entities comprising the corresponding layers on different machines are called
peers.


The peers communicate using the protocol.


No data is transferred from layer n on one machine to layer n on another machine.


Instead each layer passes data and control information to the layer immediately below it, until
the lowest layer is reached.


Below layer 1 is the
physical medium

through which actual communication occurs.


Between each pair of adjacent layers there is an

interface
.


A set of layers and protocols is called a
network architecture
.


A list of protocols used by a certain system, one protocol per layer is called a
protocol stack
.

Host 1

Physical medium

Host 2

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Layer 5 protocol

Layer 4 protocol

Layer 3 protocol

Layer 2 protocol

Layer 1 protocol

Layer 5

Layer 4

Layer 3

Layer 1

Layer 2

Layer 4/5 interface

Layer 3/4 interface

Layer 2/3 interface

Layer 1/2 interface



A message M, is produced by an
application process

running in layer 5 and is
given to layer 4 for
transmission
.


Layer 4 puts a
header

in front of the message to identify the message and passes
this result to layer 3.


Layer 3 breaks up the incoming messages into smaller units,
packets
, and adds
the layer 3 header to each packets. It decides which of the
outgoing line

to use and
passes the packet to layer 2.


Layer 2 adds the
header

and as well as the
trailer
and gives the resultant packet
to layer1.


Layer 1 passes the message received by layer2 and transmits it to physical
medium to send the message to the destination machine.


At the receiving machine the messages moves upwards, and the header and
trailers are stripped off as it progresses.


None of the headers for layers below layer n are passed up to layer n.




There is a basic difference between
virtual

and
actual

communication.


The peer processes in layer 4 use the layer 4
protocol.


This procedure is called
SendToOtherSide

and
GetFromOtherSide,
followed in virtual
communication.


But actual communication follows the
interface
protocol.




H3

H4

M1

M2

H3

H3

M2

T2

H2

M

M1

H4

H3

M

H4

H4

H3

H2

M1

T2

M1

H4

H3

T2

H2

H4

M

M

H3

M2

T2

M2

H3

H2

Layer 5 protocol

Layer 4 protocol

Layer 3 protocol

Layer 2 protocol

Source machine

Destination
machine

1

2

3

5

4

EXAMPLE INFORMATION FLOW SUPPORTING VIRTUAL COMMUNICATION IN LAYER 5