Computer Science - Unit 1 Revision (correct answers)
List two components with which the CPU works to execute program instructions. correct
answers Memory
Input and Output Devices
Describe the role of the Control Unit in the fetch-decode-execute cycle. correct answers
The control unit coordinates the actions of the computer. It sends out control signals to
other parts of the CPU and to other components of the computer.
State the function of the Program Counter. correct answers This holds the address of
the next instruction to be fetched.
State the function of the Memory Data Register (MDR). correct answers The MDR is
temporary store(buffer) for anything copied from memory.
State the function of the Accumulator. correct answers The accumulator is a temporary
store for the results of calculations carried out by the ALU.
State two components of Von Neumann's design in addition to the CPU. correct
answers Memory to store program data and instructions.
Input and output devices.
Define the term "stored program concept" correct answers A computer in which the
program instructions and the data are stored in memory.
State the role of RAM in the fetch-decode-execute cycle. correct answers RAM is where
the program instructions and data are stored until they are needed.
Describe what is meant by a register. correct answers A register is a memory location
within the CPU used to store program instructions and/or data.
Explain why cache memory is used in the CPU. correct answers The cache consists of
very fast memory and it is used to store frequently used commands and data. These
can be accessed more quickly from the cache than from the slower RAM when they are
needed.
The performance of a CPU can be improved by increasing its clock speed. Explain why
performance cannot be increased indefinitely by increasing the clock speed. correct
answers Performance cannot be improved indefinitely because the rate at which the
transistors process the instructions is limited.
There can also be a problem with the amount of heat generated by high clock speeds,
which may cause a malfunction if it cannot be dissipated.
Give one reason why cache memory is not used for RAM. correct answers Too
expensive.
, Define what is meant by an 'embedded system'. correct answers An embedded system
is a computer system built into another device in order to control it.
Identify three components of an embedded system. correct answers Processor
Memory
Input and output interfaces.
Explain the difference between 'general purpose machines' and 'embedded systems'.
correct answers Desktop computers are designed to run a range of different
applications e.g. word processors, spreadsheets etc. while each embedded system is
designed to perform a small, specific range of functions linked to the device it is
embedded into.
Explain why low-level languages such as assembly language are used for writing the
programs for embedded systems. correct answers Assembly language is used so that
the hardware can be directly controlled by the programs written. This is far more
efficient than using a high-level language that needs an interpreter or compiler.
Define what is meant by 'volatile memory'. correct answers Volatile memory provides
temporary storage for program instructions and data. It loses its content when the power
is switched off.
A computer's main memory consists of both RAM and ROM. Compare RAM and ROM.
correct answers RAM is volatile but ROM is non-volatile. RAM can be written to and
read from, but ROM can only be read from. RAM stores program instructions and data,
but ROM is used to store the sets of instruction needed for a computer to start.
State one example of data which is stored in RAM. correct answers Sets of instructions
needed for the computer to start.
Data used by a program when it is executing.
Explain what is meant by 'virtual memory'. correct answers Virtual memory is an area of
the hard disk drive or solid-state drive used as temporary RAM when the actual RAM is
full. Instructions that haven't been used recently are swapped out to virtual memory to
free up space in main memory for other instructions and data that the processor needs
immediately.
Explain why a computer sometimes needs to make use of virtual memory. correct
answers When a computer is running the operating system and several applications at
the same time, the RAM often becomes full. The OS will use virtual memory to store
some of the data, usually on the hard disk drive.
Explain how a computer's OS manages the use of virtual memory. correct answers If
there is no free memory, the OS will 'swap out' some of the data stored in RAM to the
swap area on the hard disk drive and 'swap in' the requested data to the now free area.
List two components with which the CPU works to execute program instructions. correct
answers Memory
Input and Output Devices
Describe the role of the Control Unit in the fetch-decode-execute cycle. correct answers
The control unit coordinates the actions of the computer. It sends out control signals to
other parts of the CPU and to other components of the computer.
State the function of the Program Counter. correct answers This holds the address of
the next instruction to be fetched.
State the function of the Memory Data Register (MDR). correct answers The MDR is
temporary store(buffer) for anything copied from memory.
State the function of the Accumulator. correct answers The accumulator is a temporary
store for the results of calculations carried out by the ALU.
State two components of Von Neumann's design in addition to the CPU. correct
answers Memory to store program data and instructions.
Input and output devices.
Define the term "stored program concept" correct answers A computer in which the
program instructions and the data are stored in memory.
State the role of RAM in the fetch-decode-execute cycle. correct answers RAM is where
the program instructions and data are stored until they are needed.
Describe what is meant by a register. correct answers A register is a memory location
within the CPU used to store program instructions and/or data.
Explain why cache memory is used in the CPU. correct answers The cache consists of
very fast memory and it is used to store frequently used commands and data. These
can be accessed more quickly from the cache than from the slower RAM when they are
needed.
The performance of a CPU can be improved by increasing its clock speed. Explain why
performance cannot be increased indefinitely by increasing the clock speed. correct
answers Performance cannot be improved indefinitely because the rate at which the
transistors process the instructions is limited.
There can also be a problem with the amount of heat generated by high clock speeds,
which may cause a malfunction if it cannot be dissipated.
Give one reason why cache memory is not used for RAM. correct answers Too
expensive.
, Define what is meant by an 'embedded system'. correct answers An embedded system
is a computer system built into another device in order to control it.
Identify three components of an embedded system. correct answers Processor
Memory
Input and output interfaces.
Explain the difference between 'general purpose machines' and 'embedded systems'.
correct answers Desktop computers are designed to run a range of different
applications e.g. word processors, spreadsheets etc. while each embedded system is
designed to perform a small, specific range of functions linked to the device it is
embedded into.
Explain why low-level languages such as assembly language are used for writing the
programs for embedded systems. correct answers Assembly language is used so that
the hardware can be directly controlled by the programs written. This is far more
efficient than using a high-level language that needs an interpreter or compiler.
Define what is meant by 'volatile memory'. correct answers Volatile memory provides
temporary storage for program instructions and data. It loses its content when the power
is switched off.
A computer's main memory consists of both RAM and ROM. Compare RAM and ROM.
correct answers RAM is volatile but ROM is non-volatile. RAM can be written to and
read from, but ROM can only be read from. RAM stores program instructions and data,
but ROM is used to store the sets of instruction needed for a computer to start.
State one example of data which is stored in RAM. correct answers Sets of instructions
needed for the computer to start.
Data used by a program when it is executing.
Explain what is meant by 'virtual memory'. correct answers Virtual memory is an area of
the hard disk drive or solid-state drive used as temporary RAM when the actual RAM is
full. Instructions that haven't been used recently are swapped out to virtual memory to
free up space in main memory for other instructions and data that the processor needs
immediately.
Explain why a computer sometimes needs to make use of virtual memory. correct
answers When a computer is running the operating system and several applications at
the same time, the RAM often becomes full. The OS will use virtual memory to store
some of the data, usually on the hard disk drive.
Explain how a computer's OS manages the use of virtual memory. correct answers If
there is no free memory, the OS will 'swap out' some of the data stored in RAM to the
swap area on the hard disk drive and 'swap in' the requested data to the now free area.
