Components of the CPU
Arithmetic Logic Unit - answer Carries out arithmetic operations and logical
comparisons in the processor. Acts as a gateway to the processor.
Control Unit - answer Manages execution of instructions by using control signals to
other parts of the computer. Synchronizes actions using inbuilt clock.
Memory Unit/ Primary Memory - answer Stores OS, data and software currently in use,
boot program, operations/instructions.
Data bus - answer Carries data (being read or written) between processor and other
devices.
Address bus - answer Carries address of data/ location of register (to be read or written)
from processor to other devices.
Control bus - answer Transmits control signals (from the control unit) to the rest of the
processor.
Program counter - answer Contains address of next instruction to be executed.
Memory Address Register - answerContains address of next location to be accessed in
memory. May be the address of the next instruction copied from PC OR address of next
data item to be used copied from the address part of the instruction held in the CIR.
Memory Data Register - answerContains the contents of the address specifies in the
MAR / contains all data currently being used by the processor. The contents may be an
instruction (to be passed to the CIR) or data to be used with an instruction or data to be
copied into an address.
Current Instruction Register - answerHolds the instruction while it is being decoded and
executed. The contents of MDR are copied into the CIR if it is an instruction.
Accumulator - answerHolds the results of arithmetic carried out in the ALU. All I/O goes
through accumulator.
Arithmetic Logic Unit - answer Carries out arithmetic operations and logical
comparisons in the processor. Acts as a gateway to the processor.
Control Unit - answer Manages execution of instructions by using control signals to
other parts of the computer. Synchronizes actions using inbuilt clock.
Memory Unit/ Primary Memory - answer Stores OS, data and software currently in use,
boot program, operations/instructions.
Data bus - answer Carries data (being read or written) between processor and other
devices.
Address bus - answer Carries address of data/ location of register (to be read or written)
from processor to other devices.
Control bus - answer Transmits control signals (from the control unit) to the rest of the
processor.
Program counter - answer Contains address of next instruction to be executed.
Memory Address Register - answerContains address of next location to be accessed in
memory. May be the address of the next instruction copied from PC OR address of next
data item to be used copied from the address part of the instruction held in the CIR.
Memory Data Register - answerContains the contents of the address specifies in the
MAR / contains all data currently being used by the processor. The contents may be an
instruction (to be passed to the CIR) or data to be used with an instruction or data to be
copied into an address.
Current Instruction Register - answerHolds the instruction while it is being decoded and
executed. The contents of MDR are copied into the CIR if it is an instruction.
Accumulator - answerHolds the results of arithmetic carried out in the ALU. All I/O goes
through accumulator.
