A level Computer Science Key Terms (OCR - H446)
1. ALU: 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."
2.CU: "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."
3. Register: "Tiny areas of extremely fast memory located in the CPU
normally designed for a specific purpose, where data or control
information is stored temporarily."
4. PC: Program Counter
"A register in the control unit which holds the address of the next
instruction to be executed."
5. ACC: 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."
6. MAR: 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."
7. MDR: Memory Data Register
"A register in the CPU that stores data being transferred to and from
the immedi- ate-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."
8. CIR: Current Instruction Register
,"A register in the control unit that stores the address of the next
instruction currently being executed and decoded."
9. Buses: "A common physical pathway shared by signals to and
from several components of a computer."
10.Data Bus: "A common physical pathway shared by signals to and
from several components of a computer."
,11.Address Bus: "The part of the bus which carries identification about
where the data is being sent."
12.Control Bus: "This bus carries command and control signals to and
from every other component of a computer."
13.Fetch-Decode-Execute: "The complete process of retrieving an
instruction from store, decoding it and carrying it out. Also known as
the instruction cycle."
14.CPU: Central Processing Unit
"The main part of the computer, consisting of the registers, ALU and
control unit."
15.Clock Speed: "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."
16.Cores: "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."
17.Cache: "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."
18.Pipelinning: "The concurrent decoding of two or more machine
instructions. While part of one instruction (for example, an address
field) is being decoded, another part of a second instructions (for
example, an operation code) may also be decoded."
19.Von Neumann Architecture: "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""
20.Harvard Architecture: "A computer architecture with physically
separate stor- age 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."
21.Contemporary Architecture: "Any modern set of disciplines that
, describes the functionality, the organisation and the implementation
of computer systems."
22.CISC: Complex Instruction Set Computing
"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."
1. ALU: 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."
2.CU: "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."
3. Register: "Tiny areas of extremely fast memory located in the CPU
normally designed for a specific purpose, where data or control
information is stored temporarily."
4. PC: Program Counter
"A register in the control unit which holds the address of the next
instruction to be executed."
5. ACC: 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."
6. MAR: 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."
7. MDR: Memory Data Register
"A register in the CPU that stores data being transferred to and from
the immedi- ate-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."
8. CIR: Current Instruction Register
,"A register in the control unit that stores the address of the next
instruction currently being executed and decoded."
9. Buses: "A common physical pathway shared by signals to and
from several components of a computer."
10.Data Bus: "A common physical pathway shared by signals to and
from several components of a computer."
,11.Address Bus: "The part of the bus which carries identification about
where the data is being sent."
12.Control Bus: "This bus carries command and control signals to and
from every other component of a computer."
13.Fetch-Decode-Execute: "The complete process of retrieving an
instruction from store, decoding it and carrying it out. Also known as
the instruction cycle."
14.CPU: Central Processing Unit
"The main part of the computer, consisting of the registers, ALU and
control unit."
15.Clock Speed: "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."
16.Cores: "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."
17.Cache: "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."
18.Pipelinning: "The concurrent decoding of two or more machine
instructions. While part of one instruction (for example, an address
field) is being decoded, another part of a second instructions (for
example, an operation code) may also be decoded."
19.Von Neumann Architecture: "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""
20.Harvard Architecture: "A computer architecture with physically
separate stor- age 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."
21.Contemporary Architecture: "Any modern set of disciplines that
, describes the functionality, the organisation and the implementation
of computer systems."
22.CISC: Complex Instruction Set Computing
"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."
