Fetch-Decode-Execute Cycle - Computer Science 0478 IGCSE

Which register is incremented immediately after the CPU fetches an instruction?

• MAR

• MDR

• PC

• ACC

During the fetch stage, which TWO components work together to retrieve the instruction from memory?

• A. PC and MAR

• B. ALU and ACC

• C. CU and ALU

• D. ACC and MDR

Which of the following correctly shows the order of registers involved during the fetch stage?

• MAR → PC → MDR

• PC → MAR → MDR

• MDR → MAR → PC

• PC → MDR → MAR

What is the role of the CU during the DECODE stage?

• Execute calculations

• Identify the instruction and prepare control signals

• Store results

• Fetch next instruction from memory

Which part of the CPU performs the EXECUTE stage of an arithmetic instruction?

• CU

• ALU

• PC

• MAR

What happens in the CPU if the current instruction requires data from memory?

• The CPU restarts the cycle

• The ALU sends data to the PC

• The CU uses MAR and MDR to fetch the data

• The data is stored in ROM

A student claims: “The Program Counter stores the actual instruction ready for execution.” Why is this incorrect?

• The PC stores addresses, not instructions

• The PC is replaced by MAR

• The PC executes the instruction

• The PC stores data values only

Where is the instruction stored immediately AFTER it has been fetched from memory?

• PC

• MAR

• MDR

• CU

Which of the following BEST explains why the CPU uses the fetch-decode-execute cycle repeatedly?

• It increases computer storage

• It enables multitasking

• It allows sequential execution of program instructions

• It prevents overheating of the CPU

A programmer optimizes code so that frequently used instructions fit into cache. How does this make the fetch stage faster?

• Because instructions can be accessed more quickly from cache than from main memory.

• Because it reduces the number of instructions needed to execute a program.

• Because it increases the clock speed of the processor.

• Because it allows the processor to skip the fetch stage entirely.