CD storage has an interesting take, the available sector size varies by use, i.e.
audio or MPEG1 video (VideoCD) at 2352 data octets per sector (with two media level ECCs), actual data at 2048 octets per sector where the extra EDC/ECC can be exposed by reading "raw". I learned this the hard way with VideoPack's malformed VCD images, I wrote a tool to post-process the images to recreate the correct EDC/ECC per sector. Fun fact, ISO9660 stores file metadata simultaneously in big-endian and little form (AFAIR VP used to fluff that up too).
xhkkffbf|3 months ago
theragra|3 months ago
BTW, byte size during the history varied from 4 to 24 bit! Even now, based on interpretation, you can say 16 bit bytes do exist.
Char type can be 16 bit on some DSP systems.
I was curious, so I checked. Before this comment, I only knew about 7 bit bytes.
ralferoo|3 months ago
adrian_b|3 months ago
"Octet" has the advantage that it is not ambiguous. In old computer documentation, from the fifties to the late sixties, a "byte" could have meant any size between 6 bits and 16 bits, the same like "word", which could have meant anything between 8 bits and 64 bits, including values like 12 bits, 18 bits, 36 bits, 60 bits, or even 43 bits.
Traditionally, computer memory is divided in pages, which are divided in lines, which are divided in words, which are divided in bytes. However the sizes of any of those "units" has varied in very wide ranges in the early computers.
IBM System/360 has chosen the 8-bit byte, and the dominance of IBM has then forced this now ubiquitous meaning of "byte", but there were many computers before System/360 and many coexisting for some years with the IBM 360 and later mainframes, where byte meant something else.
mrspuratic|3 months ago
FTR, ECMA-130 (the CD "yellow book" equivalent standard) is littered with the term "8-bit bytes", so it was certainly a thing then. Precision when simultaneously discussing eight-to-fourteen modulation, and the 17 encoding "bits" that hit the media for each octet as noted in a sibling comment.
Now, woktets on the other hand...
asveikau|3 months ago