Fetch Execute Cycle

Question 1

What is the fetch execute cycle?

Answer 1

• Also known as the instruction cycle, the fetch-execute cycle is the basic operation cycle of a computer
  
  • It’s the process in which a computer receives information (data) and determines what to do with said data
  • This cycle is run continuously by the central processing unit (CPU)
• The process follows four phases: fetch, decode, execute and store

Question 2

What parts of the CPU are needed?

Answer 2

ALU, CU and registers

Question 3

What does fetch mean?

Answer 3

• The CPU collects an instruction and prepares it for decoding
• The instruction is collected from a memory location.

Question 4

What does decode mean?

Answer 4

• The decoder in the control unit works out (decodes) what to do with the instruction
• Each CPU is designed to understand a specific set of commands
• These commands are referred to as the instruction set
• These instruction sets work by providing the CPU with machine code (hexadecimal or binary instructions)

Question 5

What does execute mean?

Answer 5

• The Arithmetic Logic Unit (ALU) then executes the decoded instructions
• These instructions can be arithmetic (manipulation of numbers) or logical processes
• The data from the fetch phase of the cycle is manipulated according to the instructions received from the program
• All the steps above can be seen as prerequisites for the execute phase

Question 6

What does store mean?

Answer 6

• Send and write the results back in main memory.
• The newly processed data is then passed back in to memory fresh from its processing via the data bus. The data can be re-submitted for further processing or be used for a practical use, such as reporting and other outputs