What Does "64-bit Operating System" Mean?

By Warren Davies

64-bit processors moved computing past the 4GB memory limit.
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Some recently released operating systems are referred to as "64-bit" systems. Windows Vista and Windows 7 are both available in 64-bit incarnations, as is Snow Leopard for the Mac. These 64-bit systems are gradually replacing the older 32-bit systems because of their greater ability to access and manage the computer's memory. This allows 64-bit systems to run faster and handle more intensive processes. An understanding of 64-bit system begins with a knowledge of the basic unit of computing data -- the bit.


A "bit," short for binary digit, is the simplest unit of data that computers process. It can be either 0, or 1, and all computer data at its simplest level is made up of strings of 0s and 1s. The number of bits that a computer can deal with at any time is called the "word size." The larger the word size, the larger the number that can be represented in 0s and 1s, allowing more and larger data files to be processed at the same time.

32-bit Systems

With a string of 32-bits, a number as high as 4,294,967,295 can be represented. In practical terms, this means that in a 32-bit operating system, the amount of memory is limited by this word size, which works out at around 4GB. So if the computer hardware such as graphics cards takes up half of that, for example, this only leaves 2GB of free memory available for the operating system to use. This essentially limits the performance of the computer.

64-bit Systems

A 64-bit system can access far more RAM than the 4GB of the 32-bit systems. A 64-bit system can access 17.2 billion gigabytes of memory. This is way ahead of the requirements of present day hardware and software applications, and means that the devices connected to the system are not using memory that the operating system would ordinarily use. Essentially, 64-bit systems are faster than their 32-bit counterparts, and they are "future-proofed" for a long time to come.


In order to use a 64-bit operating system, your computers hardware must be compatible. The primarily concern is the processor, which must be 64-bit itself, otherwise the operating system will not work. Beyond this, 64-bit device drivers must be installed for all hardware connected to the computer. In terms of software, programs are available that allow applications produced for 32-bit systems to run smoothly on 64-bit systems, such as WoW64 for Windows.