Four distinct actions machine instruction can specify:
It is used when the process of execution involves transfer of information from processor to memory (or) from memory to processer.
It is used when the process of execution involves transfer information between the I/O module and processor, when the information read from the I/O device.
3. Data processing:
The processor performs some logical or arithmetic actions on the data or information.
It is used to control the sequence of instructions.
For example, processor fetches an instruction from the location 900, now processor need to fetch the instruction in location 920 rather than 901. Therefore PC of the processor set to 920.execution when an instruction came to the processor.