4.7.1.1 Internal hardware components Quiz: AQA Computer Science, Unit 7

The 20 questions

1. Which bus carries the memory location that the processor wants to read or write?

   • The control bus, which carries read and write requests between components
   • The address bus is bidirectional and so carries data in both directions
   • The address bus
   • The data bus, which carries the values being read from or written to memory

2. Which statement describes the control bus?

   • It carries the actual data values being transferred between the processor and memory
   • It carries control signals such as read and write requests and timing signals between components
   • It carries the electrical power supply from the mains to each individual component
   • It carries the memory addresses from the processor to main memory only

3. Which feature is characteristic of the von Neumann architecture?

   • Instructions and data share the same main memory and the same bus structure
   • It is used mainly in digital signal processing systems in embedded devices
   • It has no control unit, because the instructions are executed directly from the bus
   • Instructions and data are held in separate memories, each with its own bus

4. Which type of system typically uses a Harvard architecture processor?

   • Embedded systems such as digital signal processing systems
   • Laptops that share main memory with the integrated graphics processor
   • Mainframe computers running large transaction-processing database systems
   • General-purpose desktop computers running office software and web browsers

5. A processor has an address bus of 16 lines and each memory location holds one byte. How many distinct locations can it address?

   • 65,536 (2^16)
   • 32,768 (2^15)
   • 16,384 (2^14)
   • 131,072 (2^17)

6. A computer has 32 address lines and is byte addressable. What is the largest amount of memory it can directly address?

   • 32 GB, because each address line addresses one gigabyte
   • 4 GB (2^32 bytes)
   • 2 GB, because one address line is reserved for the status register
   • 4 MB, because the address bus width is measured in megabytes

7. A system uses a 20-line address bus with byte addressing. How many addressable memory locations does this give?

   • 2,097,152 (2^21)
   • 1,000,000 (10^6), because addresses are counted in decimal
   • 524,288 (2^19)
   • 1,048,576 (2^20)

8. Which component holds the programs and data that the processor is currently using?

   • The status register, which holds the flags for the most recent operation
   • Main memory (RAM)
   • The control unit, which keeps the current program stored in its circuits
   • Secondary storage such as a hard disk or solid-state disk

9. Why do computers use buses rather than a separate wire between every pair of components?

   • Buses remove the need for addressable memory, because each device is identified by its data
   • Buses let main memory store instructions without any processor being present in the machine
   • A shared set of lines reduces the number of connections needed and lets components use a common protocol
   • Buses are faster than direct wires because they bypass the system clock entirely

10. Which statement describes a disadvantage of the von Neumann architecture?

    • It cannot run general-purpose software, so it is limited to special-purpose embedded devices
    • It cannot store programs in main memory, so every instruction must be typed in again
    • Instructions and data share one memory and path, which can limit how fast both can be transferred
    • It needs a separate memory for each data type, which makes it expensive to manufacture

11. A processor has a 32-bit data bus and must read a 64-bit value from memory. How many separate data bus transfers are needed?

    • 2
    • 1
    • 4
    • 8

12. Which statement about addressable memory is correct?

    • Each location stores exactly one character regardless of what the data represents
    • Only secondary storage uses addresses, because main memory is accessed by content instead
    • Locations are identified by the values stored in them rather than by any address
    • Each memory location has a unique address, and the processor uses that address to read or write the location

13. A program needs 200,000 bytes of memory, and the computer uses byte addressing. What is the minimum number of address lines needed?

    • 17 (2^17 gives 131,072 locations, which is still less than 200,000 bytes)
    • 20 (2^20 gives over a million locations, more than the program requires)
    • 16 (2^16 gives 65,536 locations, which is far too few for this program)
    • 18 (2^17 is 131,072, which is too small, while 2^18 is 262,144)

14. A system uses separate buses for instructions and data, as in a Harvard architecture. Which advantage results?

    • Fewer address lines are needed, because data and instructions can share the same addresses
    • The processor no longer needs a control unit, because the buses co-ordinate themselves
    • An instruction fetch and a data access can take place at the same time, which can improve throughput
    • Instructions can be modified more easily, because they share the same memory as the data

15. What is the role of the processor in a computer system?

    • It manages the wireless connection to the network and nothing else in the machine
    • It stores programs permanently so that they are available when the power is switched off
    • It converts analogue signals from sensors into digital form for the display to show
    • It fetches, decodes and executes instructions and performs arithmetic and logic operations

16. Which bus carries the signal that tells memory whether to perform a read or a write?

    • The control bus
    • The status register, which holds the flags for the last operation
    • The address bus, which carries the location to be read or written
    • The data bus, which carries the value to be read or written

17. Which component connects peripheral devices such as a keyboard and printer to the rest of the computer?

    • The status register of the processor, which records each device's state
    • Main memory, which stores the input data as it arrives
    • An I/O controller
    • The control bus alone, without any device hardware attached to it

18. A computer has a 64-bit data bus and a 40-line address bus. Which statement is correct?

    • It can address 2^104 locations, because the two bus widths are added together
    • It can address 2^40 locations, and each data transfer moves 64 bits
    • It can address 40 locations and moves 40 bits in each data transfer
    • It can address 2^64 locations, because the data bus is wider than the address bus

19. Which statement best compares main memory with secondary storage?

    • Main memory is non-volatile and slower than a hard disk, so it keeps its data when the power is switched off
    • Secondary storage is accessed directly by the processor and holds only the instruction that is currently executing
    • Main memory holds files permanently, and it costs less per gigabyte than a hard disk drive does in most systems
    • Main memory is directly accessible by the processor and is volatile, whereas secondary storage keeps data when powered off

20. A processor writes a value to memory location 0x0040. Which buses carry the location, the value and the write request, in that order?

    • Address bus, data bus, control bus
    • Address bus, control bus, data bus
    • Control bus, data bus, address bus
    • Data bus, address bus, control bus

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