1027030
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BTECH 7-12
- LESSON 7
- WWW
- Tim Berners Lee
-1991
- consists of millions of
web pages linked
together and content
that appears on them
- subset of the internet; consists of
web pages that can be accessed
using a web browser. Internet is
network where all info sits
- Tim Berners Lee
-1991
- HTML
- hypertext markup
language
- HTML Tags
- normally in pairs - operating tag
(<body>) and end tag (/). content
between pairs is HTML element
- e.g. <html> - opening tag for program
</body> - end tag for section
- normally in pairs - operating tag
(<body>) and end tag (/). content
between pairs is HTML element
- hypertext markup
language
- URL
- Uniform Resource Locator
- Uniform Resource Locator
- WWW
- LESSON 8
- Store & forward
- sender & recipient don't have to be online at
same time. sender sends message , it's stored
on an email server and waits there until
recipient signs in, when server forwards
message to them.
- sender & recipient don't have to be online at
same time. sender sends message , it's stored
on an email server and waits there until
recipient signs in, when server forwards
message to them.
- Fields
- To field- where you enter email address
- Cc field (Carbon copy) - recipients
entered are visible to everyone
- Bcc field (Blind Carbon Copy) -
recipient isn't visible to everyone
- To field- where you enter email address
- E-mail
- speed of delivery,
cost, instant, multiple
recipients, attachments
- privacy & security, internet
access, lack of interactivity
- speed of delivery,
cost, instant, multiple
recipients, attachments
- Protocols
- SMTP - Simple Mail transfer protocol
- used to send messages across networks in server-to-sever transfers.
- used to send messages across networks in server-to-sever transfers.
- POP3 - Post Office Protocol 3
- used to retrieve emails from email server over TCP connection.
- used to retrieve emails from email server over TCP connection.
- IMAP - Instant Message Access Protocol
- another email retrieval protocol
- another email retrieval protocol
- SMTP - Simple Mail transfer protocol
- Store & forward
- LESSON 9
- CODEC
- device/ program used
to encode/decode data.
- device/ program used
to encode/decode data.
- Transmission modes
- Simplex
- sends data in one direction
only e.g. computer to printer
- sends data in one direction
only e.g. computer to printer
- Half Duplex
- two-way transmissions but not at
the same time e.g. walkie talkies
- two-way transmissions but not at
the same time e.g. walkie talkies
- Duplex
- two-way communication at the
same time e.g. telephone system
- two-way communication at the
same time e.g. telephone system
- Simplex
- Transmission methods
- wired
- UTP/STP
e.g. analogue
telephone
network
- twisting cancels out interference, low cost and adaptable
- slower with less capacity than other cables, short distances, susceptible to noise
- twisting cancels out interference, low cost and adaptable
- Coaxial
e.g.
aerial/dish
connection
to TV
- fast and reliable
- costs more than UTP/STP, susceptible to noise
- fast and reliable
- Fibre Optic
- fasts, works over long distance, little interference
- complex
equipment needed
- fasts, works over long distance, little interference
- UTP/STP
e.g. analogue
telephone
network
- wireless
- Infrared
- reliable
- short range, devices must be in direct line
of sight, can suffer external interference
- reliable
- Microwave
- signal degrades
little over long
distances
- devices must be in direct
line of sight, can be
affected by sun, rain, pollen
and external interference
- signal degrades
little over long
distances
- Satellite
- can increase
distance a
network can reach
- expensive
- can increase
distance a
network can reach
- Infrared
- wired
- CODEC
- LESSON 10
- transmissions
- simple
- bits transmitted one at a time
over single wire/ channel.
reduces cost, but slower rate
of data transfer. bytes have to
be diassembled and
reassembled before/ after
transmission. can be used
over large distances
- bits transmitted one at a time
over single wire/ channel.
reduces cost, but slower rate
of data transfer. bytes have to
be diassembled and
reassembled before/ after
transmission. can be used
over large distances
- Parallel
- number of bits of data can be
transmitted at the same time over equal
no. of wires/ channels, Allows bits in
whole byte of info to be transmitted
together. short range (max. 5m)
- number of bits of data can be
transmitted at the same time over equal
no. of wires/ channels, Allows bits in
whole byte of info to be transmitted
together. short range (max. 5m)
- bi-directional
- transmitting in both
directions. Light
passes in 1 direction
only, so you have to
add extra fibres to the
bundle to carry a
signal in the opposite
direction
- transmitting in both
directions. Light
passes in 1 direction
only, so you have to
add extra fibres to the
bundle to carry a
signal in the opposite
direction
- simple
- client side processing
- when he interaction
between a web page and
code occurs directly on a
user's computer
- speed, security
- it's browser specific,
computer speed
- speed, security
- when he interaction
between a web page and
code occurs directly on a
user's computer
- server side processing
- when the interaction
between a web page
and a computer is
processed through a
server
- efficiency, browser
independant, speed
- security, overloading
- efficiency, browser
independant, speed
- when the interaction
between a web page
and a computer is
processed through a
server
- USB
- Universal serial bus -
higher speed serial
connection standard
that supports low and
higher speed devices
- Universal serial bus -
higher speed serial
connection standard
that supports low and
higher speed devices
- transmissions
- LESSON 12
- key points
- malware
- hostile, intrusive or
annoying piece of software
or program code
- hostile, intrusive or
annoying piece of software
or program code
- threats to data
- oppurtunist
- people find unattended
computer which is logged on
and view, steal or damage
info, programs or hardware
- people find unattended
computer which is logged on
and view, steal or damage
info, programs or hardware
- virus
- small programs which replicate
and spread between computers.
NOT beneficial - make some
changes to the system and are
undesirable. attach themselves to
files/ emails
- small programs which replicate
and spread between computers.
NOT beneficial - make some
changes to the system and are
undesirable. attach themselves to
files/ emails
- trojan
- phishing
- attempts to gain access to passwords, financial
details and other privileged info. done by emails
pretending to come from trusted websites etc. try to
divert you to a website which looks original and asks
for info about you
- attempts to gain access to passwords, financial
details and other privileged info. done by emails
pretending to come from trusted websites etc. try to
divert you to a website which looks original and asks
for info about you
- oppurtunist
- accidental damage
- can be caused by natural disasters
e.g. flooding, mischief or accidental
mishap. can result in losing all of a
computer's data
- can be caused by natural disasters
e.g. flooding, mischief or accidental
mishap. can result in losing all of a
computer's data
- malware
- attack consequences
- organisations' reputation damaged
- puts customers off, lose money
- organisation's secrets spread to competitors
- don;t have advantage anymore
- identity theft
- disclosure of info could cause legal problems - companies can be sued
- organisations' reputation damaged
- puts customers off, lose money
- preventative actions
- physical barrier
- e.g turn of computer, lock office
- e.g turn of computer, lock office
- Password
- sequence of characters which allow access
to computers, networks or applications
- sequence of characters which allow access
to computers, networks or applications
- access levels
- allow individuals to have access
only to specific levels of application
- allow individuals to have access
only to specific levels of application
- anti-virus software
- intercept computer viruses
before they become resident
- intercept computer viruses
before they become resident
- firewall
- software which monitors
all data arriving - stops
anything that is harmful
- software which monitors
all data arriving - stops
anything that is harmful
- encryption
- codifies data so can't be
read by people who don;t
have key to code.
- codifies data so can't be
read by people who don;t
have key to code.
- physical barrier
- key points
- LESSON 11
- data storage
- holding data on a computer system
- holding data on a computer system
- database structure
- Table
- or grid - data about a particular thing
- or grid - data about a particular thing
- Record
- row - holds info about a single item
- row - holds info about a single item
- fields
- or column - holds info about properties of items
- or column - holds info about properties of items
- data type
- Text
- Number
- date/ time
- logical
- currency
- Text
- Table
- relationships
- can be ONE-TO-ONE,
ONE-TO-MANY, or
MANY-TO-MANY
- primary key
- unique record that identifies each individual record
- unique record that identifies each individual record
- Foreign Key
- keyfield from another
table within the table to
link them together
- keyfield from another
table within the table to
link them together
- can be ONE-TO-ONE,
ONE-TO-MANY, or
MANY-TO-MANY
- data storage
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