Fetch-Execute Cycle

Question 1

What is ‘Von Neumann Architecture’?

Answer 1

When program instructions and data are stored in the same memory. Memory is accessed via the same bus.

Question 2

Summarise the Fetch-Execute Cycle

Answer 2

The Fetch-Execute Cycle consists of each instruction within a program being read one at a time into the CPU from program memory and then decoded and performed.

Question 3

What 3 main components are part of the Fetch-Execute Cycle?

Answer 3

The CPU, Memory and Buses.

Question 4

What is meant by ‘Fetch’?

Answer 4

Read the ‘next’ instruction from memory. The ‘next’ instruction is determined by the Program Counter.

Question 5

What is meant by ‘Decode’?

Answer 5

Make sense of what needs to be done.

Question 6

What is meant by ‘Execute’?

Answer 6

Do the task, such as arithmetic, storing, making decisions, etc.

Question 7

What is the Program Counter?

Answer 7

The Program Counter holds the address of the next instruction to fetch. Each value in the Program Counter represents an address.

Question 8

What is the Instruction Register?

Answer 8

The Instruction Registry holds the current instruction being decoded. It is where it is interpreted by the decoder component of the Control Unit.

Question 9

What is the Arithmetic and Logic Unit?

Answer 9

The ALU performs all the arithmetic needed for operations.

Question 10

What are General Registers?

Answer 10

A very fast but expensive way to store data.

Question 11

What is the Memory Address Register (MAR)?

Answer 11

The MAR holds the address of the current instruction that is to be fetched from memory, or the address of where data is to be transferred.

Question 12

What is the Memory Data Register? (MDR)

Answer 12

The MDR holds the contents found at the address held in the MAR, or data that is to be transferred to primary storage. Where values/instructions are stored before they are used by the CPU.

Question 13

Describe the Fetch-Decode-Execute Cycle

Question 14

What is the Opcode?

Answer 14

What do we need to do. The Opcode is a part of an instruction that tells the CPU what should be done. It includes the data to be acted on, or the memory location of the data in a register.

Question 15

What is the Operand?

Answer 15

What do we need to do it to. Either the value that the instruction uses or manipulates, or the address where that data is found.

Question 16

What are Instructions?

Answer 16

The set of commands/codes in machine language used to tell the CPU what to do next.

Question 17

What is the Accumulator?

Answer 17

The Accumulator is primarily used as a register that stores intermediate logical or arithmetic data in multistep calculations. Essentially a temporary storage location while the other numbers are retrieved.