Question

I’m a bit confused about bit architectures. I just cant find a good article that answers my questions, so I figured I’d ask SO.

Question 1:

When speaking of a 16 bit architecture, does it mean each ram address is 16 bits long? So if I create an int (32 bit) in C++ the variable would take up 2 addresses?

Question 2:

in a 16 bit architecture there are only 2^16 (65536) amount of addresses inside the RAM. Why can’t they add more? Is this because 16 bit can’t represent a higher value and therefore can’t reference to adresses above 65535?

Answer 1

When speaking of a 16 bit architecture, does it mean each ram address is 16 bits long? So if I create an int (32 bit) in C++ the variable would take up 2 addresses?

You’d have to ask whoever was speaking of a 16-bit architecture what they meant by it. They could mean addresses are 16-bits long. They could mean general-purpose CPU registers are 16-bits long. They could mean something else. But there’s no way we could know what some hypothetical person might mean. There is no universal definition of what makes something a “16-bit architecture”.

For example, the 8032 is an 8-bit architecture with 8-bit general purpose registers. But it has a 16-bit pointer register that can be used to address 65,536 bytes of storage.

Regardless of bitness, almost all systems use byte addresses. So a 32-bit variable will take up 4 addresses on a machine of any bitness.

in a 16 bit architecture there are only 2^16 (65536) amount of addresses inside the RAM. Why can’t they add more? Is this because 16 bit can’t represent a higher value and therefore can’t reference to adresses above 65535?

With 16-bits, there are only 65,536 possible ways those bits can be set. So a 16-bit register has 65,536 possible values.