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The size of the byte has historically been hardware dependent and no definitive standards existed that mandated the size.

The de facto standard of eight bits is a convenient power of two permitting the values 0 through 255 for one byte.

With ISO / IEC 80000-13, this common meaning was codified in a formal standard.

Many types of applications use variables representable in eight or fewer bits, and processor designers optimize for this common usage.

The popularity of major commercial computing architectures have aided in the ubiquitous acceptance of the 8-bit size.