This interesting article by PC Magazine discusses the history and evolution of computing from 32 bit to 64 bit addressability.

http://www.pcmag.com/article/350934/32-bit-vs-64-bit-oses-whats-the-difference

Keep going exponentially and you eventually get 32-bit (2 to the 32nd power) worth 4,294,967,296; 64-bit (or 2 to the 64th power) is worth 18,446,744,073,709,551,616 values.  That’s a lot of bits, and the numbers show just how much more powerful a chip that supports higher bit computing can be. It’s a lot more than double. That’s because every few years, the chips inside the computers (even smartphones) and the software running on those chips make leaps forward in supporting a new number. For example:

*  The Intel 8080 chip in the 1970s supported 8-bit computing.
*  Windows 3.1 back in 1992 was the first 16-bit desktop version of Windows.
*  AMD shipped the first 64-bit desktop chip in 2003.
*  Apple made Mac OS X Snow Leopard entirely 64-bit in 2009.
*  The first smartphone with a 64-bit chip (Apple A7) was the iPhone 5s in 2014.

It’s pretty obvious: 64-bit, sometimes styled as x64, is capable of doing more than 32-bit (which is actually called x86, a term that stuck from when Windows Vista starting sticking 32-bit apps in a folder called “Program Files (x86),” x86 originally referring to any OS with the instruction set to work on Intel chips like 8086 through 80486).

These days, you are most likely already running 64-bit chips with 64-bit operating systems, which in turn run 64-bit apps (for mobile) or programs (on the desktop, to settle on some nomenclature). But not always. Windows 7, 8, 8.1, and 10 all came in 32-bit or 64-bit versions, for example. If you are running Windows on a computer less than 10 years old, your chip is almost guaranteed to be 64-bit, but you may have installed a 32-bit version of the OS. It’s easy enough to check.