BTEC ICT Revision - Teach Me Computing

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Html is made up of tags. The majority of them
will be in pairs.
Some of the most common tags are shown
below.
Tags
What does this mean?
<b>
Bold
<i>
Italic
<p>
Paragraph
<img>
Image
<a href>
Hyperlink
<li>
List
<ul>
bullet
A page will be set out like the following.
<html>
<body>
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</body>
</html>
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Web Crawlers/Spiders are the same thing.
These are small automated programs(or bots)
that carry out processes all the time without
Human involvement. They are constantly
moving around the internet, finding new
pages. When they find a new page they log it in
an indexed database which the search engines
will use to populate results.
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Packet switching is the process of data being
broken into packets to be sent through a
network and then reassembled at the other
end. This method is used on the internet.
See diagram page 22 in revision booklet.
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Voip uses CODECs at either end to encode and
decode data.
So Mr Cole records a message using a webcam
and microphone. This is converted(encoded)
into digital data which is then broken down
into packets and sent across the internet.
Once it reaches the other end it is reassembled
into it a complete digital form, and the decoded
so the person can view the video and sound.
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Simplex
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Full duplex
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Data goes in one direction at a time (Remote)
Signals go in both directions at the same time
(Smartphone)
Half Duplex
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Signals go in both directions but don’t transmite at
the same time (printer)
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Parallel connection means simultaneous
transmission of N bits. These bits are sent
simultaneously over N different channels (a
channel being, for example, a wire, a cable or
any other physical medium). The parallel
connection on PC-type computers generally
requires 10 wires.
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Benefit
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Faster as more bits are transferred per second
Limitation
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Overall short distance (maximum of a 5 meter cable)
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In a serial connection, the data are sent one bit
at a time over the transmission channel.
However, since most processors process data
in parallel, the transmitter needs to transform
incoming parallel data into serial data and the
receiver needs to do the opposite.
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Benefit
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Good over large distances
Limitation
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Complex as the data has to be broken into individual
bits
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Pop – Point of Presence
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NAP – Network Access Point
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Takes data from the TCP (Transmission Control Protocol)
Organises it into packets
Routes it across the network and puts the packets back in the correct order at the
other end.
FTP – File Transfer Protocol
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Takes data from the users application
Passes it to the internet protocol.
(The reverse happens at the other end)
IP – Internet Protocol
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Different networks interconnect, such as your home network connecting the internet.
TCP – Transmission Control Protocol
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Is an access point to the internet. An ISP may have several PoPs to allow good access
to the internet.
FTP is the protocol which allows files to be transferred between two computers or
devices. It is usually used to download or upload large files to a server.
HTTP – HyperText transfer Protocol
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It is a protocol that allows you to request web pages and download them to our
computers.
Emaail is known as a STORE and FORWARD System.
POP3, IMAP and SMTP are all communication protocols
used when sending and receiving emails.
SMTP
Simple Mail
Transfer
Protocol
‘Push’ pushes
the mail from
the server to
the client.
POP3
Post office
Protocol 3
‘pull’ pulls the
mail from the
server to client
when
requested.
IMAP
Internet
Used for
Message Access webmail
protocol
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See Page 26 – revision guide
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See page 27 revision guide
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