The maximum number of memory and I/O devices that can be addressed in a 8085 microprocessor based system is 216. Let's break down the explanation into the following sections:

1. Address Bus:
The 8085 microprocessor has a 16-bit address bus, which means it can address a maximum of 2^16 = 65,536 memory locations. These memory locations can be used to address both memory and I/O devices.

2. Memory Addressing:
In a microprocessor-based system, a portion of the address space is reserved for memory. The remaining address space is used for I/O devices. In the case of the 8085 microprocessor, the memory address space ranges from 0000H to FFFFH (64KB).

3. Memory Devices:
The memory devices that can be connected to the 8085 microprocessor can include RAM (Random Access Memory) and ROM (Read-Only Memory). RAM is used for temporary storage of data, while ROM is used for permanent storage of program instructions.

4. I/O Devices:
The I/O devices that can be connected to the 8085 microprocessor can include input devices (such as keyboards and sensors) and output devices (such as displays and actuators). These devices are used to communicate with the external world.

5. Addressing Limitation:
Since the 8085 microprocessor has a 16-bit address bus, it can address a maximum of 2^16 = 65,536 memory locations. However, some of these memory locations are reserved for memory devices, leaving a smaller address space for I/O devices.

6. Calculation:
To calculate the maximum number of I/O devices that can be addressed, we need to subtract the number of memory locations from the total address space. Since the memory address space ranges from 0000H to FFFFH (64KB), the number of memory locations is 64KB.

Total addressable locations = 2^16 = 65,536
Number of memory locations = 64KB = 64 * 1024 = 65,536

Therefore, the maximum number of I/O devices that can be addressed = Total addressable locations - Number of memory locations = 65,536 - 65,536 = 0

7. Conclusion:
Based on the above calculation, the maximum number of memory and I/O devices that can be addressed in a 8085 microprocessor based system is 216, which means no additional I/O devices can be addressed beyond the memory address space.