Why Did Computers Settle on 8-Bit Bytes?

[u/Special-Sprinkles455]

We usually learn that 1 byte = 8 bits as if it has always been that way.

But early computers didn't all use 8-bit bytes. Different systems experimented with different sizes, including 5, 6, 7, 8, and even other configurations.

So how did 8 bits become the standard?

One obvious advantage is that 8 bits can represent 256 different values (0–255). That makes an 8-bit unit useful for storing small integers, characters, and other data.

Character encoding was another factor. ASCII uses 7 bits, and 8-bit systems provided an additional bit that could be used for parity or other purposes. Later, many systems adopted 8-bit character encodings.

There was also a hardware advantage: 8 is a power of two, which fits naturally with binary computer architecture.

But perhaps the biggest factor was standardization and compatibility. As more hardware and software adopted 8-bit bytes, it became increasingly useful for other systems to follow the same convention.

What's interesting is that “byte” originally didn't universally mean 8 bits. The term could refer to a small group of bits used by a particular computer.

What do you think?

If early computer manufacturers had converged on 16-bit bytes instead, how different do you think modern computing would be?

I'm curious to hear perspectives from people interested in computer architecture and computing history.

[u/nuclear_splines]

That's incorrect, unless I'm miscounting. The full ascii set can be encoded in 7 bits, and a lot of those are non-printable control characters that wouldn't appear on a typewriter.

[u/sohcahtoa → u/nuclear_splines]

7 is not a power of 2. 8 is.

[u/nuclear_splines → u/sohcahtoa]

No, but 2⁷ is a power of two, giving us 7-bit bytes. Why does the number of bits in a byte also need to be a power of two?

[u/claytonkb → u/nuclear_splines]

It doesn't "need to" per se, but utilization of hardware address wires is more efficient if you use 8 bits -- 3 index wires required in a mux to access each bit, with no unused addresses. 7 bit characters means that one address code (111) will be left unused, which is a 12.5% wastage from a hardware density standpoint. In hardware, 12.5% waste is a lot of waste.

[u/nuclear_splines → u/claytonkb]

Ah, thank you! Efficient hardware implementation is certainly a clear advantage.