2. Data transmission
A section of Computer Science, 0478
Listing 10 of 82 questions
Four 7-bit binary values are transmitted from one computer to another. A parity bit was added to each binary value creating 8-bit binary values. All the binary values have been transmitted correctly. Tick (3) to show whether an Even or an Odd parity check has been used for each binary value. 8-bit binary value Even (3) Odd (3) A parity check may not always detect errors that have occurred in data transmission. State why a parity check may not detect data transmission errors. Give one other error checking method that could be used to check for errors in data transmission.
0478_w20_qp_13
THEORY
2020
Paper 1, Variant 3
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Five statements are given about the error-checking methods checksum, check digit and parity check. Tick (3) to show whether each statement applies to checksum, check digit or parity check. Some statements may apply to more than one error-checking method. Statement Checksum (3) Check digit (3) Parity check (3) uses an additional bit to create an odd or even number of 1s checks for errors on data entry compares two calculated values to see if an error has occurred will not detect transposition errors sends additional values when data is transmitted from a computer to another Identify one other error-checking method.
0478_w21_qp_11
THEORY
2021
Paper 1, Variant 1
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Five statements are given about error-checking methods. Tick (3) to show whether each statement applies to Automatic Repeat reQuest (ARQ), check digit or checksum. Some statements may apply to more than one error-checking method. Statement ARQ (✔) Check digit (✔) Checksum (✔) checks for errors on data entry uses a process of acknowledgement and timeout compares two calculated values to see if an error has occurred may resend data until it is confirmed as received checks for errors in data after transmission from a computer to another Identify one other error-checking method.
0478_w21_qp_13
THEORY
2021
Paper 1, Variant 3
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Errors can occur when data is transmitted. Give one reason an error may occur when data is transmitted. Some error detection methods use a calculated value to check for errors. Tick (3) one box to show which error detection method does not use a calculated value to check for errors. A Check digit B Checksum C Echo check D Parity check An automatic repeat request (ARQ) can be used to make sure that data is received free of errors. It can use a positive or negative acknowledgement method to do this. Explain how an ARQ operates using a positive acknowledgement method.
0478_w23_qp_13
THEORY
2023
Paper 1, Variant 3
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A barcode scanning system uses a check digit to check for errors in data on input. Explain how the barcode scanning system operates to check for errors. After a barcode is scanned, data is sent to a stock control system to update the stock value stored for that product. The data is sent to the stock control system using serial simplex data transmission. Explain how the data is sent using serial simplex data transmission. Explain why serial simplex is the most appropriate method of data transmission for this purpose. The data is checked for errors after it has been transmitted to the stock control system. Give two error detection methods that could be used for this purpose.
0478_w24_qp_12
THEORY
2024
Paper 1, Variant 2
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A self-driving tractor sows seeds and harvests crops for a farmer. The self-driving tractor moves automatically through the field, turning at each end and stopping when it has finished. One reason the self-driving tractor is a robot is because it has a mechanical structure that includes wheels, an engine, and a framework. Give one other reason why the self-driving tractor is an example of a robot. If a person is detected within 3 metres whilst the tractor is moving, the self-driving tractor must stop. Explain how an infra-red sensor, microprocessor and actuator can be used to stop the self-driving tractor if a person is detected within 3 metres. Identify one other sensor that the self-driving tractor might use and how it will use the sensor. Sensor Use Explain the drawbacks of a farmer using a self-driving tractor to sow seeds and harvest crops. The self-driving tractor has an in-built expert system that the farmer can use to solve any errors with the tractor. Identify three components of an expert system. At the end of each day the self-driving tractor transmits the data it has collected to the farmer’s computer in their house. The transmission uses an echo check. Describe the role of the self-driving tractor and the farmer’s computer in the echo check. Another method of error checking is a parity block check. The table shows 7 bytes that are transmitted using odd parity. The parity bit has been completed for each byte. Complete the parity byte for the data. parity bit bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7 parity byte
0478_m24_qp_12
THEORY
2024
Paper 1, Variant 2
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Check digits are used to ensure the accuracy of entered data. A 7-digit number has an extra digit on the right, called the check digit. digit position: digit: – – – – – – – – check digit The check digit is calculated as follows: • each digit in the number is multiplied by its digit position • the seven results are then added together • this total is divided by 11 • the remainder gives the check digit (if the remainder = 10, the check digit is Calculate the check digit for the following number. Show all your working. 4 2 4 1 5 0 8 … Check digit An operator has just keyed in the following number: 3 2 4 0 0 4 5 X Circle below correct if the check digit is correct OR incorrect if the check digit is incorrect. correct incorrect Explain your answer.
0478_s16_qp_11
THEORY
2016
Paper 1, Variant 1
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Check digits are used to ensure the accuracy of entered data. A 7-digit number has an extra digit on the right, called the check digit. digit position: digit: – – – – – – – – check digit The check digit is calculated as follows: • each digit in the number is multiplied by its digit position • the seven results are then added together • this total is divided by 11 • the remainder gives the check digit (if the remainder = 10, the check digit is Calculate the check digit for the following number. Show all your working. 4 2 4 1 5 0 8 … Check digit An operator has just keyed in the following number: 3 2 4 0 0 4 5 X Circle below correct if the check digit is correct OR incorrect if the check digit is incorrect. correct incorrect Explain your answer.
0478_s16_qp_13
THEORY
2016
Paper 1, Variant 3
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The three binary numbers in the registers given have been transmitted from one computer to another. One binary number has been transmitted incorrectly. This can be identified by the use of a Parity bit. Identify the binary number that has been transmitted incorrectly. Explain how you identified the incorrect binary number. Parity bit Register A Register B Register C The binary number that has been transmitted incorrectly is in Register Explanation
0478_s19_qp_13
THEORY
2019
Paper 1, Variant 3
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Questions Discovered
82