AQA AS COMPUTER SCIENCE 7516/2 Paper 2
Stored program concept - ANSWER Instructions and data first have to be loaded
into main memory (from secondary storage if necessary) before they can be fetched,
decoded and executed by the processor.
Von Neumann architecture - ANSWER Main memory used to store all of the data
and instructions needed by the processor which can be accessed via buses.
Instructions and data are treated the same.
Harvard architecture - ANSWER Main memory physically split into two parts (one to
store data and the other to store instructions). There are separate wires from the
processor to each of the two parts. Instructions and data are treated differently.
Random access memory (RAM) - ANSWER Volatile (loses contents after power is
removed) and contents can be easily changed. This is a chip/collection of chips
made up of memory cells.
Read only memory (ROM) - ANSWER Non-volatile, contents normally can't be
changed. Stores basic, important instructions (e.g. embedded systems, BIOS
settings).
Application software - ANSWER Programs that do things humans would like to do.
This includes text editing programs, spreadsheet software, numerical software,
drawing software, sound recording software and presentation software.
Utility program - ANSWER Perform general housekeeping tasks - and can be
supplied with the operating system, or obtained elsewhere. They enhance your
experience/usage of the computer, but generally aren't required to run other
programs.
Library program - ANSWER Similar to utility but they are essential to the operating
system and other software. This includes code, data and resources called by other
programs e.g. Dynamic link libraries. (e.g. file explorer)
Translators - ANSWER Convert code in one programming language into another
programming language. The CPU can only execute machine code, whereas
programmers prefer to write in another language.
Compiler - ANSWER Programs which translate high-level language into machine
code by translating all of the code in one go.
Assembler - ANSWER Programs that translate a program written in assembly code
into machine code.
Interpreter - ANSWER Programs which translate high-level languages by reading
each statement in the source code and immediately performing the action.
, Operating system software - ANSWER Acts as a layer, between the hardware and
the other software (e.g. Windows10, the Mac OS, iOS, Android, Linux
Data Bus - ANSWER Data is transmitted along this bus, hence it is bi-directional,
i.e. signals can be transmitted in both directions (all components will need some data
to be sent to them) to and from main memory and to and from I/O controllers.
Control Bus - ANSWER Bi-directional, used to send control signals to the registers
(in the processor) as well as the data and address buses. These control signals
ensure the correct data is being transmitted to the right place at the right time (i.e.
they are self-checks of the system).
Address Bus - ANSWER This is used for specifically carrying memory addresses. It
is uni-directional, i.e. one way.
Clock - ANSWER Generates a continuous signal which synchronises all the
components, to make sure they are sending the right signals at the right time.
Control Unit - ANSWER Controls/manages/supervises the execution of any
instructions (in essence, it manages the whole Fetch-Decode-Execute cycle).
Arithmetic Logic Unit - ANSWER Can carry out arithmetic (add, subtract, ... ) and
logic operations (e.g. compare two values and return TRUE if the first is bigger than
or equal to the second, and FALSE otherwise).
Registers - ANSWER Small storage locations which hold intermediate data. These
are inside the processor so they can be accessed very quickly.
Program counter - ANSWER This holds the memory address of the next instruction
to be executed.
Current Instruction register - ANSWER This holds the current instruction being
executed.
Memory Address Register - ANSWER Holds the memory address from which data
(or an instruction) is to be fetched or to which data is to be written.
Accumulator - ANSWER Holds the output of any calculation done by the arithmetic
logic unit.
Memory Data Register - ANSWER Temporarily holds the data which is read
from/being written to the main memory. It is sometimes called the memory buffer
register [MBR].
Clock Speed - ANSWER Indicates how fast the CPU can run. This is measured in
megahertz (MHz) or gigahertz (gHz) and corresponds with how many instruction
cycles the CPU can deal with in a second. A 2 gHz CPU performs two billion cycles
a second.
Stored program concept - ANSWER Instructions and data first have to be loaded
into main memory (from secondary storage if necessary) before they can be fetched,
decoded and executed by the processor.
Von Neumann architecture - ANSWER Main memory used to store all of the data
and instructions needed by the processor which can be accessed via buses.
Instructions and data are treated the same.
Harvard architecture - ANSWER Main memory physically split into two parts (one to
store data and the other to store instructions). There are separate wires from the
processor to each of the two parts. Instructions and data are treated differently.
Random access memory (RAM) - ANSWER Volatile (loses contents after power is
removed) and contents can be easily changed. This is a chip/collection of chips
made up of memory cells.
Read only memory (ROM) - ANSWER Non-volatile, contents normally can't be
changed. Stores basic, important instructions (e.g. embedded systems, BIOS
settings).
Application software - ANSWER Programs that do things humans would like to do.
This includes text editing programs, spreadsheet software, numerical software,
drawing software, sound recording software and presentation software.
Utility program - ANSWER Perform general housekeeping tasks - and can be
supplied with the operating system, or obtained elsewhere. They enhance your
experience/usage of the computer, but generally aren't required to run other
programs.
Library program - ANSWER Similar to utility but they are essential to the operating
system and other software. This includes code, data and resources called by other
programs e.g. Dynamic link libraries. (e.g. file explorer)
Translators - ANSWER Convert code in one programming language into another
programming language. The CPU can only execute machine code, whereas
programmers prefer to write in another language.
Compiler - ANSWER Programs which translate high-level language into machine
code by translating all of the code in one go.
Assembler - ANSWER Programs that translate a program written in assembly code
into machine code.
Interpreter - ANSWER Programs which translate high-level languages by reading
each statement in the source code and immediately performing the action.
, Operating system software - ANSWER Acts as a layer, between the hardware and
the other software (e.g. Windows10, the Mac OS, iOS, Android, Linux
Data Bus - ANSWER Data is transmitted along this bus, hence it is bi-directional,
i.e. signals can be transmitted in both directions (all components will need some data
to be sent to them) to and from main memory and to and from I/O controllers.
Control Bus - ANSWER Bi-directional, used to send control signals to the registers
(in the processor) as well as the data and address buses. These control signals
ensure the correct data is being transmitted to the right place at the right time (i.e.
they are self-checks of the system).
Address Bus - ANSWER This is used for specifically carrying memory addresses. It
is uni-directional, i.e. one way.
Clock - ANSWER Generates a continuous signal which synchronises all the
components, to make sure they are sending the right signals at the right time.
Control Unit - ANSWER Controls/manages/supervises the execution of any
instructions (in essence, it manages the whole Fetch-Decode-Execute cycle).
Arithmetic Logic Unit - ANSWER Can carry out arithmetic (add, subtract, ... ) and
logic operations (e.g. compare two values and return TRUE if the first is bigger than
or equal to the second, and FALSE otherwise).
Registers - ANSWER Small storage locations which hold intermediate data. These
are inside the processor so they can be accessed very quickly.
Program counter - ANSWER This holds the memory address of the next instruction
to be executed.
Current Instruction register - ANSWER This holds the current instruction being
executed.
Memory Address Register - ANSWER Holds the memory address from which data
(or an instruction) is to be fetched or to which data is to be written.
Accumulator - ANSWER Holds the output of any calculation done by the arithmetic
logic unit.
Memory Data Register - ANSWER Temporarily holds the data which is read
from/being written to the main memory. It is sometimes called the memory buffer
register [MBR].
Clock Speed - ANSWER Indicates how fast the CPU can run. This is measured in
megahertz (MHz) or gigahertz (gHz) and corresponds with how many instruction
cycles the CPU can deal with in a second. A 2 gHz CPU performs two billion cycles
a second.
