The word size is one of the most widely used terms in computer architecture. The term “word size” refers to the number of bits a computer processes at a time.
- More specifically, it refers to the number of bits the CPU of a computer processes in a single cycle.
The most well-known word sizes are 32bit and 64bit. The older generations will also be very well acquainted with 16bit word sizes.
- The word size may also be referred to as word width or word length.
Word size in computer architecture
We can see the use of word size in numerous places in computer architecture. These concepts use either a word size or a multiple of the word size as their size. [word-tech]
- Addresses
- Fixed-point numbers
- Floating-point numbers
- Registers
- Instructions
Why word size is important?
The importance of the word size gets increased as we get closer to the computer hardware. While in high-level programming languages, it is not much of a concern to take the word size into account, in assembly language, it is a vital concept.
For example, in case we are loading some piece of data to the registers, we need to know the size of the registers to store the data properly.
Evolution of word size
The confusing part of the word size terminology is the different interpretations found in the literature. While we may encounter the word size being defined as 16bits, we also see it as 64bits in different contexts.
The evaluation of word size can be summarized as follows [word-tech]:
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, the 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.
Summary
“Word size” refers to the number of bits processed by a computer’s CPU in one go (these days, typically 32 bits or 64 bits). Data bus size, instruction size, and address size are usually multiples of the word size. [word-kof]
Modern processors, including embedded systems, usually have a word size of 8, 16, 32, or 64 bits, while modern general-purpose computers usually use 32 or 64 bits. [word-say]
References
[word-wiki]Wikipedia Contributors, “Word (computer architecture),” Wikipedia, Apr. 26, 2022. https://en.wikipedia.org/wiki/Word_(computer_architecture) (accessed Jun. 03, 2022).
[word-kof] kofhearts, “What does it mean by word size in computer?,” Stack Overflow, Nov. 06, 2013. https://stackoverflow.com/questions/19821103/what-does-it-mean-by-word-size-in-computer (accessed Jun. 03, 2022).
[word-say] “CS201: Words in Computer Architecture | Saylor Academy,” Saylor Academy, 2020. https://learn.saylor.org/mod/page/view.php?id=18960 (accessed Jun. 03, 2022).
[word-tech] Techopedia, “Word Size,” Techopedia.com, Jul. 15, 2015. https://www.techopedia.com/definition/10071/word-size (accessed Jun. 03, 2022).