Consider the following statements associated with memory mapped I/O scheme of communication with microprocessor:
1. It reduces the memory space available.
2. Arithmetic or logical operation can be directly performed with I/O data.
3. The processor cannot manipulate I/O data residing in interface registers with the same instructions that are used to manipulate memory location.
4. The processor on treats an interface register as a part of the memory system.
Which of the statements given above is/are not correct?