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CISA EXAM-Testing Concept-Check Digit,Parity Bit & Atomicity

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Testing Concept-Check Digit, Parity Bit & Atomicity

Hemang Doshi

CISA, ACA,DISA,FIII

Details about this E-Book:

This book deals with three important concepts that invariably find place in almost all CISA exams i.e Check Digit, Parity Bit and Atomicity. The objective of this e-book is to ensure that CISA candidate get adequate knowledge on these concepts. Question Answer and Explanation (QAE) are designed in accordance with CISA exam pattern.

Concepts have been simplified for easy reference of CISA candidates.

Check Digit:

 

A check digit is a mathematically calculated value that is added to data to ensure that the original data have not been altered. This helps in avoiding transposition and transcription errors.

 

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.

#
p<>{color:#000;}. Add the odd number digits: 6+0+0+2+1+5 = 14.

#
p<>{color:#000;}. Multiply the result by 3: 14 × 3 = 42.

#
p<>{color:#000;}. Add the even number digits: 3+0+0+4+4 = 11.

#
p<>{color:#000;}. Add the two results together: 42 + 11 = 53.

#
p<>{color:#000;}. 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.

 

Parity Bits:

 

The parity method of error detection is quite simple and simply requires adding an extra bit on the data. This extra bit is called a parity bit. This bit simply says whether the number of 1 bits is odd or even. Generally the parity bit is 1 if the number of 1 bits is odd and 0 if the sum of the 1 bits is even.

 

This parity is verified by receiving computer to ensure data completeness and data integrity during transmission.

 

Parity bits are used to check for completeness of data transmissions. A parity check is a hardware control that detects data errors when data are read from one computer to another, from memory or during transmission.

 

Checksum:

 

Checksums are exactly same as parity but able to identify complex errors also by increasing the complexity of the arithmetic.

 

Cyclic Redundancy Checksums (CRC)/Redundancy Checksums:

 

More advanced version of checksums by increasing the complexity of the arithmetic.

 

Forward Error Control:

 

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

 

Atomicity:

 

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. The principle of atomicity requires that a transaction be completed in its entirety or not at all. If an error or interruption occurs, all changes made upto that points are backed out.

 

 

 

 

Point to remember for CISA exam:

 

table<>. <>. |<>.
p<>{color:#000;}. Objective |<>.
p<>{color:#000;}. Relevant Control | <>. |<>. | <>. |<>.
p<>{color:#000;}. To identify transcription & transposition errors (accuracy) |<>.
p<>{color:#000;}. Check Digit | <>. |<>.
p<>{color:#000;}. To identify data transmission error (completeness & integrity) |<>.
p<>{color:#000;}. (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.

<>.
<>.

 

 

(1)When objective is to identify transcription and transposition error, answer should be check digit.

 

(2)When objective is to ensure accuracy, answer should be check digit.

 

(3)When objective is to identify transmission error, answer should be parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).

 

(4)When objective is to ensure completeness, answer should be parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).

 

(5)When objective is to ensure integrity, answer should be parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).

 

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

 

(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.

 

(7)When objective is to correct (detect & correct) transmission error, answer should be Forward Error Control (FEC).

 

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

 

 

Question, Answer & Explanation on ‘Check Digit-Parity Bit-Atomicity’ Concept:

Below QAE are solely on the concept of parity bits, check digit and atomicity. They resemble to the type/nature of questions as per CISA exam pattern. Candidates are advised to attempt below questions multiple times. More emphasis to be given on explanation part for better understanding.

 

(1)An IS auditor should recommend which of following check (control) for completeness of data transmission?

 

A. Check digits

B. One-for-one checking

C. Parity bits

D. Atom City

 

Answer: C. Parity bits

 

Explanation:

When objective is to identify transmission error, relevant control out of above options is parity bits. A parity check is a hardware control that detects data errors when data are read from one computer to another, from memory or during transmission. Parity bits are used to check for completeness of data transmissions.

Objective of check digit is to identify transcription and transposition error.

 

 

(2)An IS auditor should suggest which of the following data validation edits for banks to avoid transposition and transcription errors and thereby ensuring the correctness of bank account numbers assigned to customers?

 

A. Parity check

B. Checksum

C. Check digit

D. Existence check

 

Answer: C. Check digit

 

Explanation:

When objective is to identify transcription and transposition error, best validation control is check digit. A check digit is a mathematically calculated value that is added to data to ensure that the original data have not been altered. This helps in avoiding transposition and transcription errors. Bank uses check digit to check for accuracy.

 

 

(3)An IS auditor is reviewing a process where frequency of transposition and transcription errors are very high for data entry. Which of the following data validation edits will be effective in detecting such errors?

 

A. Parity check

B. Duplicate check

C. Validity check

D. Check Digit

 

Answer: D. Check Digit

 

Explanation:

Check digit is effective in detecting transposition and transcription errors. A check digit is a mathematically calculated value that is added to data to ensure that the original data have not been altered. This helps in avoiding transposition and transcription errors. Parity bit is used to detect data transmission error.

 

A validity check helps to validate the data in accordance with predetermined criteria.

 

Duplicate check helps to prevent data duplication.

 

(4) An IS auditor is reviewing EDI application and observed that validation edit ‘checksum’ has been implemented for communication of financial transactions. Purpose of ‘checksum’ is to ensure:

 

A. source validation.

B. authenticity.

C. integrity.

D. non-repudiation.

 

Answer: C. integrity.

 

Explanation:

Checksum is used for data integrity and data completeness. Extra bit is added to the data while data transmission. This bit is verified by receiving computer to ensure data completeness and data integrity during transmission. Thus a checksum calculated on an amount field and included in the EDI communication can be used to identify unauthorized modifications.

 

Source validation and authenticity cannot be established by a checksum alone and need other controls.

 

Non-repudiation can be ensured by using digital signatures.

(5)Principle of data integrity that a transaction is either completed in its entirety or not at all is known as:

 

A. atomicity.

B. consistency.

C. isolation.

D. durability.

 

Answer: A. atomicity.

 

Explanation:

Following is the concept of ACID (atomicity, completeness, isolation and durability) principle for data integrity:

 

Atomicity:

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. The principle of atomicity requires that a transaction be completed in its entirety or not at all. If an error or interruption occurs, all changes made upto that points are backed out.

 

Consistency:

Consistency ensures that all integrity conditions in the database be maintained with each transaction.

 

Isolation:

Isolation means that each transaction is separated from other transactions.

 

Durability:

Durability means that the database survives failures (hardware or software).

 

 

(6)Main reason for implementing parity bits as a control is to validate:

 

A. Data source

B. Data completeness

C. Data availability

D. Data accuracy

 

Answer: B. Data completeness

 

Explanation:

Parity bits are a control used to validate data completeness. The parity method of error detection is quite simple and simply requires adding an extra bit on the data. This extra bit is called a parity bit. This bit simply says whether the number of 1 bits is odd or even. Generally the parity bit is 1 if the number of 1 bits is odd and 0 if the sum of the 1 bits is even.

This parity is verified by receiving computer to ensure data completeness and data integrity during transmission.

Parity bits are used to check for completeness of data transmissions. A parity check is a hardware control that detects data errors when data are read from one computer to another, from memory or during transmission.

 

(7) Which of the following control BEST detects transmission error by appending extra bits onto the end of each segment?

 

A.Checksum

B. parity check

C. redundancy check

D. check digits

 

Answer: C. redundancy check.

 

Explanation:

Parity check, checksum and redundancy check detects transmission error by appending extra bits. How CRC/Redundancy check is best method to detect transmission error as it applies advanced arithmetic calculation.

 

Please note, when objective is to ensure completeness, control should be either parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum) with following preferences for BEST detection:

 

(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.

 

(8)Detection of bursts of errors in network transmissions is Best ensured by:

 

A. Parity check

B. Echo check

C. Checksum

D. Cyclic redundancy check

 

Answer: D. Cyclic redundancy check

 

Explanation:

Parity check, checksum and redundancy check detects transmission error by appending extra bits. How CRC/Redundancy check is best method to detect transmission error as it applies advanced arithmetic calculation.

 

The cyclic redundancy check (CRC) can check for a block of transmitted data. The workstations generate the CRC and transmit it with the data. The receiving workstation computes a CRC and compares it to the transmitted CRC. If both of them are equal, then the block is assumed error free.

 

(9)To ensure detection and correction of errors, redundant information is transmitted with each character or frame. This control is known as:

 

A. Parity bits

B. block sum check

C. forward error control

D. cyclic redundancy check

 

Answer: C. forward error control.

Explanation:

When objective is to correct (detect & correct) transmission error, best control will be Forward Error Control (FEC).Forward error control involves transmitting additional redundant information with each character or frame to facilitate detection and correction of errors. Other controls help to detect the error, but automatic correction will not happen.

 

 

(10) An IS auditor is reviewing a ERP system. To evaluate data integrity he should review atomicity to ensure that:

 

A. hardware or software failure will not impact the database.

B. each transaction is isolated from other transactions.

C. database consistency is maintained.

D. a transaction is completed in its entirety.

 

Answer: D. a transaction is completed in its entirety.

 

Explanation:

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. The principle of atomicity requires that a transaction be completed in its entirety or not at all. If an error or interruption occurs, all changes made upto that points are backed out.

 

This concept is included in the atomicity, completeness, isolation and durability (ACID) principle. Durability means that the database survives failures (hardware or software). Isolation means that each transaction is separated from other transactions. Consistency means that integrity conditions are maintained.

 

(11) An IS auditor is reviewing EDI application and observed that validation edit ‘Check Digit’ has been implemented for financial transactions. Purpose of ‘Check Digit’ is to:

 

A. Detect only data-transcription errors

B. Detect data-transposition and transcription errors

C. Detect data-transmission error.

D. Detect only data-transposition errors

 

Answer: B. Detect data-transposition and transcription errors

 

Explanation:

A check digit is an effective edit check to detect data-transposition and transcription errors.

 

 

 


CISA EXAM-Testing Concept-Check Digit,Parity Bit & Atomicity

Details about this E-Book: This book deals with three important concepts that invariably find place in almost all CISA exams i.e Check Digit, Parity Bit and Atomicity. The objective of this e-book is to ensure that CISA candidate get adequate knowledge on these concepts. Question Answer and Explanation (QAE) are designed in accordance with CISA exam pattern. Concepts have been simplified for easy reference of CISA candidates.

  • Author: Hemang Doshi
  • Published: 2016-08-05 19:50:09
  • Words: 2099
CISA EXAM-Testing Concept-Check Digit,Parity Bit & Atomicity CISA EXAM-Testing Concept-Check Digit,Parity Bit & Atomicity