IBM famously introduced its CKD disk file format in the 60s; did anyone else
(other than IBMs clones including RCA) support such a disk format?
Specifically a disk format with a block (record in IBM terms) having a
variable length key field (including 0 length) and a variable length data
field. To the best of my knowledge everyone else used a fixed block (sector
to most) size on a disk volume but my knowledge of most of the BUNCH is