Practice Flashcards
Flip to reveal answersWhat are the three stages of the fetch-decode-execute cycle?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 5 Flashcards — Fetch–decode–execute
Sign up free to track progress and get spaced-repetition review schedules.
Question
What are the three stages of the fetch-decode-execute cycle?
Answer
Fetch the next instruction from memory, decode it in the control unit, then execute it — usually a calculation in the ALU. The cycle then repeats.
Question
Which registers are used during fetch?
Answer
The PC holds the address, which is copied to the MAR. Memory returns the instruction into the MDR, and it moves to the IR. The PC is then increased.
Question
When is the program counter increased, and why then?
Answer
During fetch. A jump instruction works by writing a new address into the PC during execute — increasing it afterwards would overwrite the jump.
Question
What happens during decode?
Answer
The control unit reads the instruction held in the IR, works out which operation is needed, and sends control signals to the parts that will carry it out.
Question
Which buses does a fetch use?
Answer
All three: the address bus carries the address out, the control bus carries the read signal, and the data bus brings the instruction back.
Read the notes
Full study notes for Fetch–decode–execute
Topic 1.1 hub
Hardware and operation
More from Topic 1.1
All flashcards in this topic
Computer Science exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free