Fichas
Needing For Checking Error's
Fichas del conjunto (9)
- 1Need For Checking ErrorsParity Checking,
Automatic Repeat Request,
Check Sum,
Echo Check - 2Parity CheckingParity Checking is one method used to check whether data has been changed or corrupted following transmission from one device or medium, to another device or medium.
A byte of data, for example, is allocated a PARITY BIT. This is allocated before transmission takes place. systems that use EVEN PARITY have an even number of 1-bits; system that use ODD PARITY have an odd number of 1-bits. - 3Automatic Repeat Request (ARQ)Automatic Repeat Request is another method used to check whether data has been correctly transmitted. It used an ACKNOWLEDGEMENT (A message sent by the receiver indicating that data has been received correctly) and TIMEOUT (This is the time allowed to elapse before an acknowledgement is received).
If an acknowledgement isn't sent back to the sender before timeout occurs, then the message is automatically resent. - 4Check SumCheck sum is another way to check if data has been changed or corrupted following data transmission. Data is sent in blocks and an additional value, the checksum, is also sent at the end of the block of data.
To explain how this works, we will assume the checksum of a block of data is 1 byte in length. This gives a maximum value of 28 − 1 (i.e. 255). The value 0000 0000 is ignored in this calculation. - 5Echo CheckWith Echo Check, when data is sent to another device, this data is sent back again to the sender. The sender compares the two sets of data to check if any errors occurred during the transmission process.
As you will have no doubt worked out, this isn't very reliable.
If the two sets of data are different, it isn't known whether the error occurred when sending the data in the first place, or if the error occurred when sending the data back for checking!
However, if no errors occurred then it is another way to check that the data was transmitted correctly. - 6checking errorsChecking for errors is important since computers aren't able to check that text is correct; they can only recognize whether a word is in their built-in dictionary or not.
- 7Need For Checking ErrorsWithout error handling technology, we cannot have confidence in the performance and output produced for a computer.
- 8Even and oddTwo make it an odd u need to make sure their are an odd amount of 1 for example if the sequence goes 101101 then u add another 1 to make it five one's.
To make it an even u take one away or u put a 0 if it is already has the right amount of 1's and 0's. - 9Check Sum calculationdivide the sum, X, of the bytes by 256
round the answer down to the nearest whole number
Z=Y*256
Calculate the difference (X-Z)
This value is the check sum.
Example: 1185/256= 4.629=4
4x 256= 1024
1185- 1024= 161
161 is the answer.
Información
- Descripción
- Fichas sobre Needing For Checking Error's, creado por 11.barfield el 20/10/2015.
- Creado por
- 11.barfield
- Visitas
- 0
- Valoración