Error detection

Question 1

what is parity check

Answer 1

method which involves the first digit of the byte in making the number of 1s even or odd

Question 2

If the sum of the bytes in the block is less than or equal to 255, what is the checksum

Answer 2

the value of the number

Question 3

step for checksum if the value is greater than 255

Answer 3

a. Divide the sum of the bytes in the block by 256 to get the quotient.
b. round down to the nearest integer
c. Multiply the integer value by 256 to get the product.
d. Subtract the product from the sum of the bytes to get the checksum.

Question 4

what is echo check

Answer 4

method of error detection where the receiving computer sends back an exact copy of the data to the sending computer. The sending computer then compares the data it originally sent to the data it has received back. If there is a match between the two data sets, then the transmission took place without error. If there is an error, the sending computer resends the data, and the process starts all over again.

Question 5

disadvantages of echo check

Answer 5

difficult to tell whether the data was corrupted in transit to the destination or on its way back. Another disadvantage is speed, because the complete data has to be sent twice.

Question 6

what is check digit

Answer 6

extra digit added to a number that is calculated from the existing digits in the number

Question 7

examples of check digits

Answer 7

International Standard Book Number (ISBN), product codes, barcodes and Vehicle Identification Numbers (VIN).

Question 8

step by step of table making for check digits

Answer 8

digits, multiplier (1 or 3), sum of all numbers, round down, subtract rounding from sum