Step-by-step explanation:
program counter:
- it is also known as instruction pointer.
 - it has the address of the instruction that is being executed at that time.
 
- it is a 32-bit register .
 
instruction register:
- it keeps the instruction that is being executed at that time.
 - it holds active memory that is currently executed
 
execute process:
it is based on 3 cycles: 
- fetch
 - decode
 - execute
 
fetch:
it takes the instruction from program counter(has memory address)
decode:
the instruction that is fetched is decoded/interpreted by the decoder.
execute:
The result generated by the operation is stored in the main memory or sent to an output device