3.3 CRM (Doshi)

Question 1

What is a check digit?

Answer 1

A mathematically calculated value that is added to data to ensure that the original data haS not been altered

Question 2

Why check digit?

Answer 2

This helps in avoiding transposition and transcription errors.

Question 3

Parity Bit

Answer 3

A method of error detection, it requires adding an extra bit (called parity bit) on the data.

Question 4

Why would a parity bit be used?

Answer 4

It’s received by computer to ensure data completeness and data integrity during transmission.

Question 5

Parity check

Answer 5

Is a hardware control that detects data errors when data is read from:

(1) one computer to another,
(2) from memory
(3) or during transmission.

Question 6

Checksums

Answer 6

• Programs that compute checksums can be run against old and new databases to ensure the accuracy of migrated data.
• Checksum ensure is data copied is the same as original

Question 7

Cyclic Redundancy Checksums (CRC)/Redundancy Checksums

Answer 7

A more advanced version of checksums by increasing the complexity of the arithmetic

Question 8

Forward Error Control

Answer 8

Works on same principle as CRC. However FEC also corrects the error. FEC provides the receiver with the ability to correct errors.

Question 9

Atomicity:

Answer 9

Atomicity is a feature of databases systems where a transaction must be all-or-nothing.

(That is, the transaction must either fully happen, or not happens at all.)

Question 10

When should a check digit be performed?

Answer 10

(1) When the objective is to identify transcription and transposition error.
(2) When the objective is to ensure accuracy,

Question 11

What relevant controls MUST be performed when the objective is to identify transmission error?

Answer 11

(1) First preference is CRC
(2) If no CRC, them checksum,
(3) If no CRC and no checksum,
(4) Then, parity bit

Question 12

What relevant controls are required to perform when objective is to ensure completeness?

Answer 12

First preference is CRC
If no CRC, them checksum,
If no CRC and no checksum,
Then, parity bit

Question 13

What relevant control should be performed when the objective is to ensure integrity?

Answer 13

First preference is CRC
If no CRC, them checksum,
If no CRC and no checksum,
Then, parity bit

Question 14

What relevant control should be performed when the objective is to correct (detect &correct) a transmission error?

Answer 14

Forward Error Control (FEC)

Question 15

When should atomicity be performed?

Answer 15

To ensure that a transaction must either fully happen, or not happens at all.

Question 16

Check digit example:

Answer 16

Example:
Check digit is used by bank to ensure the correctness of bank account numbers assigned to customers, thereby helping to avoid transposition and transcription errors.
For instance, a bank account number is “630000241457”. The last digit is the check digit “7”, and if the other numbers are correct then the check digit calculation must produce 7.
Add the odd number digits: 6+0+0+2+1+5 = 14.
Multiply the result by 3: 14 × 3 = 42.
Add the even number digits: 3+0+0+4+4 = 11.
Add the two results together: 42 + 11 = 53.
To calculate the check digit, take the remainder of (53 / 10), and if not 0, subtract from 10. Therefore, the check digit value is 7.

Question 17

When objective is to identify transcription and transposition error, answer should be

Answer 17

check digit.

Question 18

When objective is to ensure accuracy, answer should be

Answer 18

check digit.

Question 19

When objective is to identify transmission error, answer should be

Answer 19

parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).

Question 20

When objective is to ensure completeness, answer should be

Answer 20

parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).

Question 21

When objective is to ensure integrity, answer should be

Answer 21

parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).

Question 22

For point no. (3), (4) and (5), first preferences to be given as follow:

Answer 22

(i) First preference to CRC
(ii) If CRC is not there as option then preference to be given to Checksum
(iii) If CRC and Checksum both are not there in option then preference to be given to Parity Bits.

Question 23

When objective is to correct (detect & correct) transmission error,

Answer 23

answer should be Forward Error Control (FEC).

Question 24

When objective is to ensure that a transaction must either fully happen, or not happens at all, answer should be

Answer 24

atomicity.