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gerdesj | on: C++ proposal: There are exactly 8 bits in a byte
"1. bytes are 8 bits"

How big is a bit?

thamer | parent | next
This doesn't feel like a serious question, but in case this is still a mystery to you… the name bit is a portmanteau of binary digit, and as indicated by the word "binary", there are only two possible digits that can be used as values for a bit: 0 and 1.
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basementcat | parent | next
A bit is a measure of information theoretical entropy. Specifically, one bit has been defined as the uncertainty of the outcome of a single fair coin flip. A single less than fair coin would have less than one bit of entropy; a coin that always lands heads up has zero bits, n fair coins have n bits of entropy and so on.

https://en.m.wikipedia.org/wiki/Information_theory

https://en.m.wikipedia.org/wiki/Entropy_(information_theory)

fourier54 | root | parent
That is a bit in information theory. It has nothing to do with the computer/digital engineering term being discussed here.
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CoastalCoder | parent | next
> How big is a bit?

A quarter nybble.

nonameiguess | parent | next
How philosophical do you want to get? Technically, voltage is a continuous signal, but we sample only at clock cycle intervals, and if the sample at some cycle is below a threshold, we call that 0. Above, we call it 1. Our ability to measure whether a signal is above or below a threshold is uncertain, though, so for values where the actual difference is less than our ability to measure, we have to conclude that a bit can actually take three values: 0, 1, and we can't tell but we have no choice but to pick one.

The latter value is clearly less common than 0 and 1, but how much less? I don't know, but we have to conclude that the true size of a bit is probably something more like 1.00000000000000001 bits rather than 1 bit.

poincaredisk | parent
A bit is either a 0 or 1. A byte is the smallest addressable piece of memory in your architecture.
elromulous | root | parent | next
Technically the smallest addressable piece of memory is a word.
Maxatar | root | parent | next
I don't think the term word has any consistent meaning. Certainly x86 doesn't use the term word to mean smallest addressable unit of memory. The x86 documentation defines a word as 16 bits, but x86 is byte addressable.

ARM is similar, ARM processors define a word as 32-bits, even on 64-bit ARM processors, but they are also byte addressable.

As best as I can tell, it seems like a word is whatever the size of the arithmetic or general purpose register is at the time that the processor was introduced, and even if later a new processor is introduced with larger registers, for backwards compatibility the size of a word remains the same.

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asveikau | root | parent
Depends on your definition of addressable.

Lots of CISC architectures allow memory accesses in various units even if they call general-purpose-register-sized quantities "word".

Iirc the C standard specifies that all memory can be accessed via char*.

Nevermark | root | parent
Which … if your heap always returns N bit aligned values, for some N … is there a name for that? The smallest heap addressable segment?