1
OCR A LEVEL COMPUTER SCIENCE EXAM
| QUESTIONS AND ANSWERS | VERIFIED
AND WELL DETAILED ANSWERS (100%
CORRECT) | LATEST EXAM UPDATE
ALU, - (answers)Arithmetic Logic Unit: "The part of the CPU where data is
processed and manipulated. This processing and manipulation normally consists
of arithmetic operations or logical comparisons allowing a program to make
decisions."
Control Unit, - (answers)"The part of the CPU that manages the execution of
instructions. The control unit fetches each instruction in sequence, and decodes
and synchronises it before executing it by sending control signals to other parts of
the computer."
Register, - (answers)"Tiny areas of extremely fast memory located in the CPU
normally designed for a specific purpose, where data or control information is
stored temporarily."
PC, - (answers)Program Counter: "A register in the control unit which holds the
address of the next instruction to be executed."
ACC, - (answers)Accumulator: "A special register within the ALU. It is used to hold
the data currently being processed by the central processor. Any data to be
processed is stored temporarily in the accumulator, the results ending up back in
the accumulator being stored in the memory unit."
,2
MAR, - (answers)Memory Address Register: "A register in the CPU that stores the
address of the memory location currently in use. In the fetch phase, this would be
the address of the instruction being loaded; in the execute phase, it would be the
address of the data being used."
MDR, - (answers)Memory Data Register: "A register in the CPU that stores data
being transferred to and from the immediate-access store. It acts as a buffer,
allowing the central processor and memory unit to act independently without
being affected by minor differences in operation. A data item will be copied to the
MDR ready for use at the next clock pulse, when it can either be used by the
central processor or be stored in main memory."
CIR, - (answers)Current Instruction Register: "A register in the control unit that
stores the address of the next instruction currently being executed and decoded."
Busses, - (answers)"A common physical pathway shared by signals to and from
several components of a computer."
Data Bus, - (answers)"The part of the bus which carries the actual information."
Address Bus, - (answers)"The part of the bus which carries identification about
where the data is being sent."
Control Bus, - (answers)"This bus carries command and control signals to and
from every other component of a computer."
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Fetch-Decode-Execute, - (answers)"The complete process of retrieving an
instruction from store, decoding it and carrying it out. Also known as the
instruction cycle."
CPU, - (answers)Central Processing Unit: "The main part of the computer,
consisting of the registers, ALU and control unit."
Clock Speed, - (answers)"Measured in Hertz, the clock speed is the frequency at
which the internal clock generates pulses. The higher the clock rate, the faster the
computer may work. The "clock" is the electronic unit that synchronises related
components by generating pulses at a constant rate."
Cores, - (answers)"A part of a multi-core processor. A multi-core processor is a
single component with two or more independent actual CPUs, which are the units
responsibly for the fetch-decode-execute cycle."
Cache, - (answers)"A part of the main store between the central processor and
the rest of the memory. It has extremely fast access, so sections of a program and
its associated data are copied there to take advantage of its short fetch cycle."
Pipelining, - (answers)"Successive steps of an instruction sequence are executed
in turn by a sequence of cores able to operate concurrently, so that another
instruction can be begun before the previous one is finished."
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Von Neumann Architecture, - (answers)"Traditional computer architecture that
forms the basis of most digital computer systems. A single control unit manages
program control flow following a linear sequence of "fetch-decode-execute""
Harvard Architecture, - (answers)"A computer architecture with physically
separate storage and signal pathways for instructions and data. These early
machines had data storage entirely contained within the central processing unit,
and provided no access to the instruction storage as data."
Contemporary Architecture, - (answers)"Any modern set of disciplines that
describes the functionality, the organisation and the implementation of computer
systems."
CISC, - (answers)Complex Instruction Set Computer: "A design that produces a
complicated and expensive integrated circuit capable of performing a large
variety of complex instructions. Complex instructions can be executed with few
machine cycles."
RISC, - (answers)Reduced Instruction Set Computer: "A design that produces a
simple, cheap integrated circuit with a basic range of machine instructions. Relies
on speed as complex instructions take many machine cycles."
GPU, - (answers)Graphical Processing Unit: "A specialised electronic circuit
designed to rapidly manipulate and alter memory to accelerate the creation of
images in a frame buffer intended for output to a display. Modern GPUs highly
parallel structure makes them more effective than general-purpose CPUs for
algorithms where processing of large blocks of data is done in parallel."
OCR A LEVEL COMPUTER SCIENCE EXAM
| QUESTIONS AND ANSWERS | VERIFIED
AND WELL DETAILED ANSWERS (100%
CORRECT) | LATEST EXAM UPDATE
ALU, - (answers)Arithmetic Logic Unit: "The part of the CPU where data is
processed and manipulated. This processing and manipulation normally consists
of arithmetic operations or logical comparisons allowing a program to make
decisions."
Control Unit, - (answers)"The part of the CPU that manages the execution of
instructions. The control unit fetches each instruction in sequence, and decodes
and synchronises it before executing it by sending control signals to other parts of
the computer."
Register, - (answers)"Tiny areas of extremely fast memory located in the CPU
normally designed for a specific purpose, where data or control information is
stored temporarily."
PC, - (answers)Program Counter: "A register in the control unit which holds the
address of the next instruction to be executed."
ACC, - (answers)Accumulator: "A special register within the ALU. It is used to hold
the data currently being processed by the central processor. Any data to be
processed is stored temporarily in the accumulator, the results ending up back in
the accumulator being stored in the memory unit."
,2
MAR, - (answers)Memory Address Register: "A register in the CPU that stores the
address of the memory location currently in use. In the fetch phase, this would be
the address of the instruction being loaded; in the execute phase, it would be the
address of the data being used."
MDR, - (answers)Memory Data Register: "A register in the CPU that stores data
being transferred to and from the immediate-access store. It acts as a buffer,
allowing the central processor and memory unit to act independently without
being affected by minor differences in operation. A data item will be copied to the
MDR ready for use at the next clock pulse, when it can either be used by the
central processor or be stored in main memory."
CIR, - (answers)Current Instruction Register: "A register in the control unit that
stores the address of the next instruction currently being executed and decoded."
Busses, - (answers)"A common physical pathway shared by signals to and from
several components of a computer."
Data Bus, - (answers)"The part of the bus which carries the actual information."
Address Bus, - (answers)"The part of the bus which carries identification about
where the data is being sent."
Control Bus, - (answers)"This bus carries command and control signals to and
from every other component of a computer."
,3
Fetch-Decode-Execute, - (answers)"The complete process of retrieving an
instruction from store, decoding it and carrying it out. Also known as the
instruction cycle."
CPU, - (answers)Central Processing Unit: "The main part of the computer,
consisting of the registers, ALU and control unit."
Clock Speed, - (answers)"Measured in Hertz, the clock speed is the frequency at
which the internal clock generates pulses. The higher the clock rate, the faster the
computer may work. The "clock" is the electronic unit that synchronises related
components by generating pulses at a constant rate."
Cores, - (answers)"A part of a multi-core processor. A multi-core processor is a
single component with two or more independent actual CPUs, which are the units
responsibly for the fetch-decode-execute cycle."
Cache, - (answers)"A part of the main store between the central processor and
the rest of the memory. It has extremely fast access, so sections of a program and
its associated data are copied there to take advantage of its short fetch cycle."
Pipelining, - (answers)"Successive steps of an instruction sequence are executed
in turn by a sequence of cores able to operate concurrently, so that another
instruction can be begun before the previous one is finished."
, 4
Von Neumann Architecture, - (answers)"Traditional computer architecture that
forms the basis of most digital computer systems. A single control unit manages
program control flow following a linear sequence of "fetch-decode-execute""
Harvard Architecture, - (answers)"A computer architecture with physically
separate storage and signal pathways for instructions and data. These early
machines had data storage entirely contained within the central processing unit,
and provided no access to the instruction storage as data."
Contemporary Architecture, - (answers)"Any modern set of disciplines that
describes the functionality, the organisation and the implementation of computer
systems."
CISC, - (answers)Complex Instruction Set Computer: "A design that produces a
complicated and expensive integrated circuit capable of performing a large
variety of complex instructions. Complex instructions can be executed with few
machine cycles."
RISC, - (answers)Reduced Instruction Set Computer: "A design that produces a
simple, cheap integrated circuit with a basic range of machine instructions. Relies
on speed as complex instructions take many machine cycles."
GPU, - (answers)Graphical Processing Unit: "A specialised electronic circuit
designed to rapidly manipulate and alter memory to accelerate the creation of
images in a frame buffer intended for output to a display. Modern GPUs highly
parallel structure makes them more effective than general-purpose CPUs for
algorithms where processing of large blocks of data is done in parallel."
