Question

During which phase of the instruction execution cycle is the program counter incremented? a. decode b. execute c. operand fetch d. fetch

Answer 1

d. fetch

Step-by-step explanation:

A program is a set of instructions. These instructions are placed in the memory and are processed by control unit by going through some phases of instruction cycle which are fetch, decode and execute.

Fetch instruction cycle:

• At first the Program Counter PC (register) contains the address of the next instruction to be fetched.

• This address is copied to the Memory Address Register MAR.

• The address which was copied to MAR is now placed on address bus and control unit send Read command and the address is copied to the Memory Data Register MDR via the data bus.

• The contents of the MDR are then copied to Instruction Register IR.

• So the instruction is fetched.

• Now the Program Counter is incremented by 1 so that it now gets ready for the next instruction to be fetched and points to it when the next fetch instruction cycle begins.