Read the following statements about address space in microprocessors

1. An address space is a set of all possible addresses which can be generated by a microprocessor.
2. Each address in the address space allows a designer to provide at least one memory or I/O location in the system.
3. Two types of address spaces are memory and I/O address space.
4. Some micro processors have only one type of address space.

Which of the above are correct?