Question

How many times does the processor need to refer to memory when it fetches and executes an indirect-address- mode instruction if the instruction is

(a) a computation requiring a single operand

Answer 1

Fetching and executing an indirect-address-mode instruction with a single operand typically involves three memory references: one to fetch the instruction, one to fetch the operand address contained within the instruction, and one to fetch the actual operand needed for computation.

Step-by-step explanation:

When a processor fetches and executes an indirect-address-mode instruction with a computation requiring a single operand, it typically needs to refer to memory multiple times. The sequence of steps is as follows:

1. The processor fetches the instruction from memory, which constitutes one memory reference.
2. The instruction fetched contains the address of the memory location where the actual operand address is stored. The processor refers to this memory location to read the operand address, making it the second memory reference.
3. Finally, the processor refers to the memory location pointed to by the operand address to fetch the actual operand needed for the computation. This is the third memory reference.

Therefore, in total, there are three memory references made by the processor: one for instruction fetch, one for fetching the operand address, and one for fetching the operand itself.