AQA A LEVEL COMPUTER SCIENCE 7517 2
TEST BANK 2026 QUESTIONS WITH
SOLUTIONS GRADED A+
◉ What are the steps in the fetch part of the fetch-decode execute cycle
(in register transfer notation)? Answer: 1. MAR ← [PC]
2. MBR ← [Memory]addressed
PC ← [PC] + 1
3. CIR ← [MBR]
◉ What are the steps in the decode and execute parts of the fetch-decode
execute cycle? Answer: 1. Control unit splits the instruction in the CIR
into opcode and operand
2. Control unit uses opcode to identify the instruction being executed
and the part of the processor executing the instruction
3. Control unit generates necessary control signals for execution
4. Certain actions are performed depending on the instruction
,◉ What are the possible actions the processor can take in the execute
part of the fetch-decode execute cycle? Answer: -Jump/Branch
instruction -> PC is updated
-Data is required -> Memory or I/O read is issued
-Arithmetic/Logic operation -> ALU calculates results and stores in
register(s) and the status register updates to show overflow or carry
◉ What happens in the interrupt part of the fetch-decode execute cycle if
an interrupt signal of higher priority has been received by the processor?
Answer: 1. The current process being executed is suspended and the
current values of the registers are pushed to the system stack
2. The appropriate Interrupt Service Routine is found and called to
handle the interrupt
3. After the interrupt has been serviced, the original values of the
registers are retrieved from the stack and execution continues with the
instruction addressed by the PC
◉ What is an interrupt? Answer: A signal sent to the processor that
suspends execution of the current process until the interrupt is handled
with an Interrupt Service Routine (ISR)
, ◉ What sends interrupts? Answer: Hardware devices and software
programs
◉ Why do the register contents have to be pushed to the system stack
when an interrupt is received? Answer: To save the volatile environment
as the registers are going to be overwritten so the values would be lost
otherwise
◉ What does the use of interrupts allow a processor to do? Answer:
Multitask (using time slices and timer interrupts)
◉ What is hardware? Answer: The physical components of a computer
system
◉ In brief, what does the processor do? Answer: Processes data and
instructions by fetching, decoding and executing instructions in the
fetch-decode-execute cycle
◉ What is the job of the control unit in the processor? Answer: Sends
control signals and manages the fetch-decode-execute cycle in addition
to the processor as a whole
◉ What is the job of the Arithmetic Logic Unit in the processor?
Answer: Performs calculations on data it is given such as addition,
subtraction or shifting
TEST BANK 2026 QUESTIONS WITH
SOLUTIONS GRADED A+
◉ What are the steps in the fetch part of the fetch-decode execute cycle
(in register transfer notation)? Answer: 1. MAR ← [PC]
2. MBR ← [Memory]addressed
PC ← [PC] + 1
3. CIR ← [MBR]
◉ What are the steps in the decode and execute parts of the fetch-decode
execute cycle? Answer: 1. Control unit splits the instruction in the CIR
into opcode and operand
2. Control unit uses opcode to identify the instruction being executed
and the part of the processor executing the instruction
3. Control unit generates necessary control signals for execution
4. Certain actions are performed depending on the instruction
,◉ What are the possible actions the processor can take in the execute
part of the fetch-decode execute cycle? Answer: -Jump/Branch
instruction -> PC is updated
-Data is required -> Memory or I/O read is issued
-Arithmetic/Logic operation -> ALU calculates results and stores in
register(s) and the status register updates to show overflow or carry
◉ What happens in the interrupt part of the fetch-decode execute cycle if
an interrupt signal of higher priority has been received by the processor?
Answer: 1. The current process being executed is suspended and the
current values of the registers are pushed to the system stack
2. The appropriate Interrupt Service Routine is found and called to
handle the interrupt
3. After the interrupt has been serviced, the original values of the
registers are retrieved from the stack and execution continues with the
instruction addressed by the PC
◉ What is an interrupt? Answer: A signal sent to the processor that
suspends execution of the current process until the interrupt is handled
with an Interrupt Service Routine (ISR)
, ◉ What sends interrupts? Answer: Hardware devices and software
programs
◉ Why do the register contents have to be pushed to the system stack
when an interrupt is received? Answer: To save the volatile environment
as the registers are going to be overwritten so the values would be lost
otherwise
◉ What does the use of interrupts allow a processor to do? Answer:
Multitask (using time slices and timer interrupts)
◉ What is hardware? Answer: The physical components of a computer
system
◉ In brief, what does the processor do? Answer: Processes data and
instructions by fetching, decoding and executing instructions in the
fetch-decode-execute cycle
◉ What is the job of the control unit in the processor? Answer: Sends
control signals and manages the fetch-decode-execute cycle in addition
to the processor as a whole
◉ What is the job of the Arithmetic Logic Unit in the processor?
Answer: Performs calculations on data it is given such as addition,
subtraction or shifting
