On Wed, 18 May 2016 17:50:53 -0700, Charles Mills wrote: > ... It was indeed a direct access storage device. Not a disk, but DASD > nonetheless. Certainly not magnetic tape (though it had a family > resemblance!) and certainly not unit record. > What's the criterion? Max/Min latency ratio? Statistical distribution of latency between randomly selected records? For tape, it's sort of triangular; for DASD it has a sort of plateau.
Addressable by block and writable randomly without corrupting other blocks? DECtape had preformatted addressable blocks; it held a filesystem with a directory. It moved from reel to reel past a stationary R/W head. It met some criteria for DASD and some for tape; it was both. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
