What are the three main stages of the instruction cycle?
Fetch, Decode, Execute.
Which register holds the address of the next instruction?
Program Counter (PC).
During Fetch, what happens step by step?
PC → MAR (address of instruction).
Instruction read from memory → MBR.
MBR → IR (instruction loaded).
PC increments.
What is the role of the Instruction Register (IR)?
Holds the current instruction to be decoded and executed.
Which part of the CPU decodes instructions?
Control Unit (CU).
Which part of the CPU executes instructions?
ALU (for calculations/logic) or other CPU components.
What happens in the Decode stage?
CU interprets the opcode in IR and identifies required operation + operands.
What happens in the Execute stage?
The instruction is carried out: may be ALU calculation, memory access, I/O transfer, or control (like a jump).
What happens to the PC after each fetch?
: It increments to point to the next instruction, unless modified by a control instruction.
Why is the fetch–decode–execute cycle important?
It explains how the CPU repeatedly processes instructions, the fundamental operation of all stored-program computers.
