how much memory can be accessed by a 32 bit machine?

Question

What is meant by 32bit or 64 bit machine?

It’s the processor architecture…a 32 bit machine can read and write 32bit data at a time same way with 64 bit machine….

Answer 1

No your concepts are not right. And to set it right you need the answer to the question that you incorrectly answered:

What is meant by 32bit or 64 bit machine?

The answer to the question is "something significant in the CPU is 32bit or 64 bit". So the question is what is that something significant? Lot of people say the width of data bus that determine whether the machine is 32bit or 64 bit. But none of the latest 32 bit processors have 32 bit or 64 bit wide data buses. most 32 bit systems will have 36 bit at least to support more RAM. Most 64 bit processors have no more than 48bit wide data bus because that is hell lot of memory already.

So according to me a 32 bit or 64 bit machine is determined by the size of its general purpose registers used in computation or "the natural word size" used by the computer.

Note that a 32 bit OS is a different thing. You can have a 32 bit OS running on 64 bit computer. Additionally, you can have 32 bit application running on 64 bit OS. If you do not understand the difference, post another question.

So the maximum amount of RAM a processor can address is 2^(width of data bus in bits), given that the proper addressing mode is switched on in the processor.

Further note, there is nothing stopping someone to introduce a multiplex between data Bus and memory banks, that will select a bank and then address the RAM (in two steps). This way you can address even more RAM. But that is impractical, and highly inefficient.