The address space of the 8086 microprocessor is one megabyte.

Explanation:

Address space refers to the range of memory addresses that a microprocessor can access. In the case of the 8086 microprocessor, it has a maximum addressable memory of one megabyte (1 MB).

Here is a breakdown of the different address spaces in the 8086 microprocessor:

1. Physical Address Space:
- The physical address space of the 8086 microprocessor is limited to 20 bits.
- With 20 bits, the microprocessor can address a maximum of 2^20 = 1,048,576 distinct memory locations.
- Each memory location in the physical address space is represented by a unique memory address.

2. Segmented Memory Model:
- The 8086 microprocessor uses a segmented memory model.
- In this model, the 1 MB physical address space is divided into multiple segments.
- Each segment has a size of 64 kilobytes (64 KB).
- The segment registers (CS, DS, ES, SS) in the microprocessor hold the base addresses of these segments.

3. Logical Address Space:
- The logical address space is the combination of a segment address and an offset address within that segment.
- The segment address is stored in one of the segment registers, and the offset address is provided by the program.
- The logical address is converted to a physical address by combining the segment base address with the offset address.

4. Limitations:
- Although the 8086 microprocessor has a 20-bit physical address space, it can only access a maximum of 1 MB of memory.
- This limitation is due to the segmented memory model, where each segment can only be 64 KB in size.
- To access more than 64 KB of memory, the microprocessor needs to switch between different segments.

In conclusion, the address space of the 8086 microprocessor is one megabyte (1 MB), which is the maximum amount of memory that can be addressed by the microprocessor.