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2. Data transmission
A section of Computer Science, 0478
Listing 10 of 82 questions
A company owner has installed a new network. Data is correct before it is transmitted across the network. The company owner is concerned that data might have errors after transmission. Explain how the data might have errors after transmission. The company owner decides to introduce an error detection system to check the data for errors after transmission. The error detection system uses an odd parity check and a positive automatic repeat query (ARQ). Describe how the error detection system operates to check for errors. Give two other error detection methods that could be used. The company owner also installs a firewall to help protect the network from hackers and malware. Explain how the firewall operates to help protect the network. Give two examples of malware that the firewall can help protect the network from.
0478_s24_qp_11
THEORY
2024
Paper 1, Variant 1
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A file server is used as a central data store for a network of computers. Rory sends data from his computer to a file server that is approximately 100 metres away. It is important that the data is transmitted accurately. Rory needs to be able to read data from and write data to the file server at the same time. Use ticks (3) to identify the most suitable data transmission methods for this application. Method 1 Tick (3) Method 2 Tick (3) Serial Simplex Parallel Half-duplex Duplex Explain why your answer to part is the most suitable data transmission. Identify and describe two methods of error checking that can be used to make sure that the data stored after transmission is accurate. Method 1 Method 2
0478_w17_qp_12
THEORY
2017
Paper 1, Variant 2
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Data is valuable to a company. Companies use error detection methods to make sure that data is accurate. One error detection method is the use of a check digit. Explain what is meant by a check digit and how it is used to detect errors. Companies can use a range of security methods to keep their data secure. Identify two security methods that a company can use to keep their data secure and explain how each method can keep the data secure. Security method 1 Security method 2
0478_w19_qp_12
THEORY
2019
Paper 1, Variant 2
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Data is transmitted between a computer and a printer. The data is transmitted one bit at a time down a single wire. The computer can transmit data to the printer and the printer can transmit data to the computer, using the same connection. Circle the two data transmission methods that will transmit data in this way. parallel full-duplex parallel half-duplex parallel simplex serial full-duplex serial half-duplex serial simplex An odd parity check is used to detect errors in the data transmission. Explain how the odd parity check detects errors. Another error detection method sends the data from the computer to the printer, then a copy of the data received is sent back from the printer to the computer. The two sets of data are compared to see if they match. State the name of this type of error detection method.
0478_w23_qp_11
THEORY
2023
Paper 1, Variant 1
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Five computer terms and seven descriptions are shown below. Draw a line to connect each computer term to its correct description. An error detection method that uses response and time out when transmitting data; if a response is not sent back to the sender in an agreed amount of time, then the data is re-sent Several bits of data sent down several wires, in both directions, but not at the same time Serial, simplex data transmission Description Computer term Several bits of data sent down several wires, in both directions, at the same time An even or odd number of bits set to 1 in a byte, used to check if the byte has been transmitted correctly One bit sent at a time, over a single wire in one direction only An additional digit placed at the end of a number to check if the number has been entered correctly A value transmitted at the end of a block of data; it is calculated using the other elements in the data stream and is used to check for transmission errors Parallel, half-duplex data transmission Parity check Automatic repeat request (ARQ) Checksum
0478_w16_qp_11
THEORY
2016
Paper 1, Variant 1
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Five computer terms and seven descriptions are shown below. Draw a line to connect each computer term to its correct description. An error detection method that uses response and time out when transmitting data; if a response is not sent back to the sender in an agreed amount of time, then the data is re-sent Several bits of data sent down several wires, in both directions, but not at the same time Serial, simplex data transmission Description Computer term Several bits of data sent down several wires, in both directions, at the same time An even or odd number of bits set to 1 in a byte, used to check if the byte has been transmitted correctly One bit sent at a time, over a single wire in one direction only An additional digit placed at the end of a number to check if the number has been entered correctly A value transmitted at the end of a block of data; it is calculated using the other elements in the data stream and is used to check for transmission errors Parallel, half-duplex data transmission Parity check Automatic repeat request (ARQ) Checksum
0478_w16_qp_13
THEORY
2016
Paper 1, Variant 3
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Parity checks are often used to check for errors that may occur during data transmission. A system uses even parity. Tick (✓) to show whether the following three bytes have been transmitted correctly or incorrectly. Received byte Byte transmitted correctly Byte transmitted incorrectly 1 1 0 0 1 0 0 0 0 1 1 1 1 1 0 0 0 1 1 0 1 0 0 1 A parity byte is used to identify which bit has been transmitted incorrectly in a block of data. The word “F L O W C H A R T” was transmitted using nine bytes of data (one byte per character). A tenth byte, the parity byte, was also transmitted. The following block of data shows all ten bytes received after transmission. The system uses even parity and column 1 is the parity bit. letter column column column column column column column column byte 1 F byte 2 L byte 3 O byte 4 W byte 5 C byte 6 H byte 7 A byte 8 R byte 9 T parity byte One of the bits has been transmitted incorrectly. Write the byte number and column number of this bit: Byte number Column number Explain how you arrived at your answer for part . Give the denary (base 10) value of the byte: 1 0 1 1 1 1 1 0 A parity check may not identify that a bit has been transmitted incorrectly. Describe one situation in which this could occur.
0478_s15_qp_12
THEORY
2015
Paper 1, Variant 2
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Questions Discovered
82