12 terms

Fetch, Execute Cycle Terms

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Processor
Processes data and executes instructions.
MAR
The Memory Address Register holds a memory address. The memory address is provided by the Program Counter.
MDR
Once data is retrieved from Main Memory (RAM) it travels via the Data Bus to the Memory Data Register. Data/Instructions are held in the MDR temporarily. Any instructions will then be passed to the CIR.
CIR
The CIR is the Current Instruction Register. This hold the instruction that has just been fetched from main memory and is about to be executed. The Current Instruction is split into an Op Code (the operation to be performed) and the Operand (the data in which to perform the operation on).
Main Memory
Where data and Instructions currently in use are held
Address Bus
Carries addresses from the Processor to Main memory
Data Bus
Carries Data/Instructions from Main Memory back to the Processor
Accumulator
The Accumulator is used to hold the result of a calculation or an operation. When a value is inputted into the computer it will be held in the accumulator. If a value is added - then the result is temporarily held in the accumulator.
PC
The Program Counter holds the address of the next instruction that will be fetched.
ALU
Arithmetic Logic Unit - performs arithmetic (Add / Subtract) and logical (AND, OR) operations
Operand
The data in which to perform the operation on e.g. 4
Op Code
The operation to be performed e.g. LOAD
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