Word Size

Definition - What does Word Size mean?

In computing, word size refers to the maximum number of bits that a CPU can process at a time. A word is a fixed-sized piece of data which is dictated by the processor hardware architecture; fixed in a sense that it is the maximum size that the processor is always using, yet variable in the sense that word sizes vary amongst processor architectures, most notably because of generation and the state of technology.

Techopedia explains Word Size

Word size has varied in size and even in meaning throughout the history of the computer. Originally, "word" meant 16 bits, as that was the maximum possible value at the time. But as processor hardware technology progressed and computers were able to handle larger and larger amounts of data, word simply became the maximum possible number of bits that the processor in question can process. So word size could be as low as 4 bits or as high as 64 bits, depending on what a particular processor can handle.

Word size is used for a number of concepts, all relating to processing. It is used in any of the following:

  • Addresses — The address must be able to represent the full range possible, so it uses a full word or a multiple of it.
  • Fixed-point numbers — Integers are available in different sizes, but usually it takes the size of the full word supported by the processor.
  • Floating-point numbers — Holders for floating-point numbers typically use the full word size length or multiples of it.
  • Registers — The size of the register depends on the kind of register and what its purpose is, but a general-purpose register usually uses the maximum word size capability of the processor.
  • Instructions — Instruction sets for processors are often coded in full word size.
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