the Fetch-Execute cycle

The Fetch step:
This involves retrieving an instruction from a memory address. The address of the
instruction is stored in a register called the Program Counter (PC). After an instruction is
fetched, the PC is updated so the CPU knows the address of the next instruction it has to
fetch.

The Decode step:
This involves the CPU identifying the operation code (op-code) part of the instruction which
tells it which operation to perform. If the op-code requires the CPU to act on some data then
the second part of the instruction will contain either the data or the memory address where
the data is stored.

The Execute step:
The control unit links together the parts of the CPU that are needed to carry out (execute)
the instruction.

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