Everything about Data Transfer totally explained
Data transmission is the conveyance of any kind of
information from one space to another. Historically this could be done by
courier, a chain of
bonfires or
semaphores, and later by
Morse code over copper
wires.
In recent computer terms, it means sending a stream of
bits or
bytes from one location to another using any number of technologies, such as
copper wire,
optical fiber,
laser,
radio, or
infra-red light. Practical examples include moving data from one
data storage device to another such as accessing a
website, which involves data transfer from
web servers to a user's
browser.
A related concept to data transmission is the
data transmission protocol used to make the data transfer legible. Current protocols favor packet based communication.
Types of data transmission
Serial transmission bits are sent over a single wire individually. Whilst only one bit is sent at a time, high transfer rates are possible. This can be used over longer distances as a
check digit or
Parity bit can be sent along it easily.
Parallel transmission Multiple wires are used which can transmit multiple bits simultaneously, which allows for higher data transfer rates than can achieved than with Serial transmission. This method is used internally within the computer, for example the internal buses, and sometimes externally for such things as printers, The major issue with this is "skewing" because the wires in parallel data transmission have slightly different properties (not intentionally) so some bits may arrive before others, which means that the original "meaning" of the message is lost and thus leads to corruption, a
parity bit can help to reduce this. How ever parallel data transmission is therefore unsuitable for long distances (as already mentioned) because skewing is far more likely.
Asynchronous and synchronous data transmission
Asynchronous transmission uses start and stop bits to signify the beginning bit
ASCII character would actually be transmitted using 10 bits for example: A "0100 0001" would become "
1 0100 0001
0". The extra one (or zero depending on
parity bit) at the start and end of the transmission tells the receiver first that a character is coming and secondly that the character has ended. This method of transmission is used when data is sent intermittently as opposed to in a solid stream. In the previous example the start and stop bits are in bold. The start and stop bits must be of opposite polarity. This allows the receiver to recognize when the second packet of information is being sent.
Synchronous transmission uses no start and stop bits but instead synchronizes transmission speeds at both the receiving and sending end of the transmission using
clock signals built into each component. A continual stream of
data is then sent between the two nodes. Due to there being no start and stop
bits the data transfer rate is quicker although more errors will occur, as the clocks will eventually get out of sync, and the receiving device would have the wrong time that had been agreed in
protocol (computing) for sending/receiving data, so some
bytes could become corrupted (by losing
bits). Ways to get around this problem include re-synchronization of the clocks and use of
check digits to ensure the
byte is correctly interpreted and received.
Further Information
Get more info on 'Data Transfer'.
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