There are a lot of ways to count, but when it comes to computers there is only binary: 0 and 1. Each one is a considered a "bit." That means for 1-bit computing, you get two possible values; 2-bit means four values; then at 3 bits you double that to eight (2 to the third power, aka 2 cubed).
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.
How do you even tell which one you have?
Identify 64-Bit OS
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.
In Windows 10, click on the "My Computer" icon on the desktop and select "Properties" (or open the Control Panel and go to System and Security > System). Under the System heading, you'll see it at System type: "64-bit Operating System, x64-based processor" means you're covered.
You can also just type About in the Windows 10 search box to bring up the Settings page, which will show the same thing.
Why 32-Bit at All?
Why would you install a 32-bit OS on a desktop or laptop PC? The big reason is because you have a 32-bit processor, which requires a 32-bit OS.
But having such a CPU is unlikely. Intel started making 32-bit processors in the 80386 range way back in 1985; it was selling 64-bit processors by 2001. If you've bought a PC since the Pentium D chip came out in 2005, it's unlikely you'd have a 32-bit instruction set inside. The last Intel 32-bit chip, Pentium 4E, came out in February 2004 and that was extended to 64-bit by the x86-64. That was backward-compatible with both 32- and 16-bit software as needed. Later versions of the Pentium 4, like the Extreme Edition, were fully 64-bit—and even that was discontinued by 2005.
More likely, you have an old operating system you installed that only came as 32-bit. Subsequent upgrades, if any, may not have jumped up to 64-bit. And that may be fine—not all of the earliest 64-bit processors had all the features in place. You can determine if your PC is really ready for full 64-bit by using software like 64bit Checker. It works on all versions of Windows going back to Windows 95.
Installing a 32-bit OS on a 64-bit architecture system will work, but it's not optimal. A 32-bit OS, for example, has more limitations—the standout being it can only really utilize 4GB of RAM. Installing more RAM on a system with a 32-bit OS doesn't have much impact on performance. But upgrade that system with excess RAM to the 64-bit version of Windows and you'll notice the difference.
This should spell it out in the most stark way: the officially supported maximum RAM on Windows 10 is 2 terabytes (or 128GB on Windows 10 Home).
The theoretical limit of RAM at 64-bit: 16 exabytes. But we're a long way from having hardware that could ever support that.
Either way, it makes buying a new laptop with 16GB RAM not seem as impressive, doesn't it?
64-bit computing features many other improvements, though in ways that may not be noticeable to the naked eye. Wider datapaths, larger integer sizes, eight octet memory addresses. It's all stuff for the computer scientists to take advantage of to make your computing all the more powerful.
You may also notice that some programs you download for desktop operating system come in 32- and 64-bit options. Firefox is a good example, where the options are "Windows" and "Windows 64-bit" (as well as "Linux" or "Linux 64-bit"—the macOS version is 64-bit only).
Why do that? Because 32-bit OSes are still out there. They need 32-bit software to run—they typically can't even install the 64-bit versions, and certainly won't run them. However, a 64-bit OS can support a 32-bit program—Windows in particular has built in an emulation subsystem for that, called Windows32 on Windows64, or WoW64. Look in your C: drive sometime—you'll see two Program Folders: one for 64-bit programs, another called Program Folders (x86) just for 32-bit applications. You'll be kind of astounded how much 32-bit code is still out there.
On the Mac, you're less likely to find much 32-bit-ness. On the Apple menu select About this Mac, click System Report, and highlight all the applications listed under Software. Each will have a 64-bit (Intel) entry saying Yes or No. Most are going to be Yes. One holdout until recently was Microsoft Office for Mac—it only offered a 64-bit version starting in mid-2016.
Mobile 64-Bit
As noted above, Apple's A7 chip was the first 64-bit processor to go into a mobile phone (iPhone 5s). In 2015, Apple mandated that all iOS software had to go 64. So much so that as of June 2016, opening a 32-bit app in the latest versions of iOS caused a "not optimized" warning: "using it may affect overall system performance."
If you've got iOS 10, you probably can't even still use those older 32-bit apps that haven't had an update (with the exception of a few older devices supporting iOS 10 on 32-bit chips). That's the "best" thing about Apple's closed system—it can force that to happen.
On Android phones, it can be a little trickier to uncover details unless you're well-versed on what chip is inside. Also, if you're not running Android 5.0 Lollipop or newer, you're still 32-bit. One app that will tell you is AnTuTu Benchmark; load it, click the Info button, and look for the Android line. It'll tell you the Android version and if it's 32- or 64-bit. Despite there being more chips running Android, from ARM to Snapdragon, the push toward 64-bit is fully underway.
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For iOS and Android, this isn't about opening up the OS to using more RAM—the memory needs on a handheld remain negligible compared to desktop use. In fact, going x64 isn't a guarantee of better performance—plenty of Android 32-bit phones matched the initial 64-bit iPhone 5s. Plus, the first 64-bit Android phones, like the HTC Desire 510, didn't benefit at all by being stuck with an older 32-bit version of Android.
But smartphones going 64-bit has other benefits—things like fetching even more data per cycle (and faster), better encryption, and overall moving to new 64-bit chips—specifically the ARMv8 architecture—with improved features, like power efficiency.
Ultimately, the 64-bit revolution is already here on PCs and smartphones. The marketing people don't even trump it anymore. You, the consumer, don't need to know much about it to be part of it.