A computer system in a control room is used to monitor earthquake activity. An earthquake zone has a number of sensors to detect seismic activity. The system detects when seismic activity is greater than 3 on the Richter Scale. Whenever this happens, a printer in the control room prints a report. Identify the steps that are required in this monitoring system. When the system detects high activity, operators may need to respond rapidly. A printer is useful for hard copies, but may not be the best way to inform operators. Give a reason why. Name an alternative output device for this monitoring system and give a reason for your choice. Output device Reason for choice

9608_w15_qp_11

THEORY

2015

Paper 1, Variant 1

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A computer system in a control room is used to monitor earthquake activity. An earthquake zone has a number of sensors to detect seismic activity. The system detects when seismic activity is greater than 3 on the Richter Scale. Whenever this happens, a printer in the control room prints a report. Identify the steps that are required in this monitoring system. When the system detects high activity, operators may need to respond rapidly. A printer is useful for hard copies, but may not be the best way to inform operators. Give a reason why. Name an alternative output device for this monitoring system and give a reason for your choice. Output device Reason for choice

9608_w15_qp_13

THEORY

2015

Paper 1, Variant 3

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Sensors are one type of input device. For each of the following situations, name a different sensor that could be used. air conditioning in an office building maintaining correct growing conditions in a greenhouse detecting an intruder in a building Sensors are used to monitor seismic activity. At the end of each day, all the data are transmitted to a central computer. This is hundreds of kilometres away. Describe one way of ensuring that the integrity of the data is retained during the transmission stage.

9608_s15_qp_11

THEORY

2015

Paper 1, Variant 1

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Sensors are one type of input device. For each of the following situations, name a different sensor that could be used. air conditioning in an office building maintaining correct growing conditions in a greenhouse detecting an intruder in a building Sensors are used to monitor seismic activity. At the end of each day, all the data are transmitted to a central computer. This is hundreds of kilometres away. Describe one way of ensuring that the integrity of the data is retained during the transmission stage.

9608_s15_qp_12

THEORY

2015

Paper 1, Variant 2

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A company grows vegetables in a number of large greenhouses. For the vegetables to grow well, the temperature, light level and soil moisture need to always be within certain ranges. The company installs a computerised system to keep these three growing conditions within the best ranges. Sensors are used for collecting data about the temperature, light level, and moisture content of the soil. Name the type of system described. Give three items of hardware that would be needed for this system. Justify your choice. Do not include sensors in your answer. Item 1 Justification Item 2 Justification Item 3 Justification Describe what is meant by feedback in the above system. When the system was designed, various parameters for temperature were set. Name one of these parameters. Explain how this parameter value is used by the feedback system. Question 6 continues on page 14. Each greenhouse has eight sensors (numbered 1–8). • The byte at address 150 is used to store eight 1-bit flags. • A flag is set to indicate whether its associated sensor reading is waiting to be processed. • More than one sensor reading may be waiting to be processed at any particular moment. • Data received from the sensors is stored in a block of eight consecutive bytes (addresses 201–208). • The data from sensor 1 is at address 201, the data from sensor 2 is at address 202, and so on. Sensor number Interpret the current reading for sensor 2. The accumulator is loaded with the data from location 150. Write the assembly language instruction to check whether there is a value waiting to be processed for sensor 6. LDD 150 // data loaded from address 150

9608_s15_qp_33

THEORY

2015

Paper 3, Variant 3

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A gardener grows vegetables in a greenhouse. For the vegetables to grow well, the temperature needs to always be within a particular range. The gardener is not sure about the actual temperatures in the greenhouse during the growing season. The gardener installs some equipment. This records the temperature every hour during the growing season. Name the type of system described. Identify three items of hardware that would be needed to acquire and record the temperature data. Justify your choice for each. Item 1 Justification Item 2 Justification Item 3 Justification The equipment records temperatures in the greenhouse. It does this for seven locations. Each recording is stored as two successive bytes. The format is shown below: Greenhouse location Temperature reading Byte 1 Byte 2 The location is indicated by the setting of one of the seven bits in byte 1. For example, location 4 is indicated by setting bit 4. Bit 0 of byte 1 acts as a flag: • the initial value is zero • when the reading has been processed it is set to 1 Byte 2 contains the temperature reading (two’s complement integer). Interpret the data in byte 1 shown below: Byte 1 Byte 2 The system receives a temperature reading of –5 degrees from sensor 6. Complete the boxes below to show the two bytes for this recording. The reading has not yet been processed. Byte 1 Byte 2 The accumulator is loaded with the value of byte 1 from location 106. Write the assembly language instruction to check whether the reading in byte 2 came from location 4. LDD 106 // data loaded from address 106 Write the assembly language instruction to set the flag (bit 0) of the byte contained in the accumulator to 1.

9608_s15_qp_31

THEORY

2015

Paper 3, Variant 1

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A gardener grows vegetables in a greenhouse. For the vegetables to grow well, the temperature needs to always be within a particular range. The gardener is not sure about the actual temperatures in the greenhouse during the growing season. The gardener installs some equipment. This records the temperature every hour during the growing season. Name the type of system described. Identify three items of hardware that would be needed to acquire and record the temperature data. Justify your choice for each. Item 1 Justification Item 2 Justification Item 3 Justification The equipment records temperatures in the greenhouse. It does this for seven locations. Each recording is stored as two successive bytes. The format is shown below: Greenhouse location Temperature reading Byte 1 Byte 2 The location is indicated by the setting of one of the seven bits in byte 1. For example, location 4 is indicated by setting bit 4. Bit 0 of byte 1 acts as a flag: • the initial value is zero • when the reading has been processed it is set to 1 Byte 2 contains the temperature reading (two’s complement integer). Interpret the data in byte 1 shown below: Byte 1 Byte 2 The system receives a temperature reading of –5 degrees from sensor 6. Complete the boxes below to show the two bytes for this recording. The reading has not yet been processed. Byte 1 Byte 2 The accumulator is loaded with the value of byte 1 from location 106. Write the assembly language instruction to check whether the reading in byte 2 came from location 4. LDD 106 // data loaded from address 106 Write the assembly language instruction to set the flag (bit 0) of the byte contained in the accumulator to 1.

9608_s15_qp_32

THEORY

2015

Paper 3, Variant 2

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A computer receives data from a remote data logger. Each data block is a group of 8 bytes. A block is made up of seven data bytes and a parity byte. Each data byte has a parity bit using odd parity. The parity byte also uses odd parity. The following table shows a data block before transmission. Bit position 0 is the parity bit. Bit position Data bytes Parity byte A B Describe how the data logger calculates the parity bit for each of the bytes in the data block. State the two missing parity bits labelled A and B. A = B = Describe how the computer uses the parity byte to perform a further check on the received data bytes. A second data block is received as shown in the following table. There are errors in this data block. Identify and then circle two bits in the table which must be changed to remove the errors. Bit position Explain how you arrived at your answers for part .

9608_s17_qp_11

THEORY

2017

Paper 1, Variant 1

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A computer receives data from a remote data logger. Each data block is a group of 8 bytes. A block is made up of seven data bytes and a parity byte. Each data byte has a parity bit using odd parity. The parity byte also uses odd parity. The following table shows a data block before transmission. Bit position 0 is the parity bit. Bit position Data bytes Parity byte A B Describe how the data logger calculates the parity bit for each of the bytes in the data block. State the two missing parity bits labelled A and B. A = B = Describe how the computer uses the parity byte to perform a further check on the received data bytes. A second data block is received as shown in the following table. There are errors in this data block. Identify and then circle two bits in the table which must be changed to remove the errors. Bit position Explain how you arrived at your answers for part .

9608_s17_qp_13

THEORY

2017

Paper 1, Variant 3

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There are five scenarios on the left and two types of system on the right. Draw a line to link each scenario to its correct type of system. System Control Monitoring Scenario Car speed display Aeroplane autopilot Rollercoaster Recording the rainfall at a weather station Robot loading a part onto a conveyor belt Mary has six fish tanks. The temperature of the water in each tank needs to be within a specific range. Identify three items of hardware that Mary can add to her tanks to help maintain the temperature. Describe the purpose of each item. Item 1 Purpose Item 2 Purpose Item 3 Purpose A temperature reading is taken from each tank once per minute. The temperature reading is stored as two successive bytes. The format is shown: Fish tank Temperature reading Byte 1 Byte 2 The fish tank number is indicated by setting one of the bits in Byte 1 to 1. For example, fish tank number 5 is indicated by setting bit 5 to 1. Bit 7 of Byte 1 is a flag: • the flag’s initial value is zero • when the reading has been processed, the flag’s value is set to 1 Bit 0 of Byte 1 is unused. Byte 2 contains the temperature reading as a two’s complement integer. After a temperature reading has been taken, the bytes contain the following data. Byte 1 Byte 2 Analyse the data contained in the two bytes. The system receives a temperature reading of − 2 from fish tank number 4. Complete the bytes to show the values for this reading after it has been processed. Byte 1 Byte 2 A hardware device to affect the temperature of each tank is on or off depending on the value of a bit in memory location 6753. If bit 4 is 1, then the hardware device in fish tank 4 is on. Write assembly language instructions to set bit 4 of memory location 6753 to 1 without changing any other bits. Use the instruction set provided. Instruction set Instruction Explanation Op code Operand LDD Direct addressing. Load the contents of the location at the given address to ACC. STO Store the contents of ACC at the given address. AND #n Bitwise AND operation of the contents of ACC with the operand. AND Bitwise AND operation of the contents of ACC with the contents of . XOR #n Bitwise XOR operation of the contents of ACC with the operand. OR #n Bitwise OR operation of the contents of ACC with the operand. OR Bitwise OR operation of the contents of ACC with the contents of . can be an absolute address or a symbolic address.

9608_s18_qp_32

THEORY

2018

Paper 3, Variant 2

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