Welcome to the Prefix wars [WAS:RE: Weekly Classic Computer Trivia Question (20141205)]

Fred Cisin cisin at xenosoft.com
Mon Dec 8 22:11:38 CST 2014

On Mon, 8 Dec 2014, Tom Gardner wrote:
> Thanks for the comments but I still content the mess really started with
> binary sense without any qualification.  There is no doubt that K and M were
> used in a binary sense before Macintosh, but AFAIK not by any OS for disk
> capacity.
> MSDOS and PCDOS AFAIK did not use any prefixes - the utilities just reported
> the values in a string of decimal digits without commas.  Interesting but
> not surprising that CPM used binary K on memory but  I doubt it reported on
> disk capacity using any prefixes, but I could be wrong.  Don't know about
> TRS80 and PET but I doubt the OSes used prefixes of any sort.

CP/M reported disk capacity (STAT) as "K"; (STAT DSK:) as "Kilobyte"

TRS80 reported memory in K.  (1979?)  ALthough FREE reported disk free
space in "GRANS"

XT P.O.S.T. reported memory in K
In MS-DOS/PC-DOS 2.00 and above, FDISK reported hard disk capacity in
honest binary Megabytes of 1,048,576

Other than MS-DOS/PC-DOS 2.00 and above, it is true that few "8 bit"
computers ever mentioned "Megabytes"

> The real mess started when an OS reported a disk drive advertised in
> conventional MB using binary MB e.g. an ST225 advertised by Seagate as
> having 21.4 million bytes but reported by an OS as having a 20910 KB
> capacity (41,820 512 byte sectors per Seagate spec = 21.411.840 bytes = 21.4
> MB).  Where is the missing 490 KB?   Macintosh OS System 1 is the first OS
> that I know about.

WHAT missing 490 KB??!?
I recall Seagate referring to the ST225 as "20 Megabyte" (~1985?)
Unlike some other manufacturers, they rounded DOWN, not UP,
AND they did not use excessive "significant digits".
(That also gave them a lot more slack than their less scrupulous
competitors to cover bad sectors)
((In apthecary measures, there are THREE Scruples in every DRAM!))

BUT, if you are talking about the discrepancy of an OS using Binary MB,
while marketing was using Decimal MB, then FDISK in MS-DOS/PC-DOS 2.00
certainly far predates the Macintosh latecomer.

Macintosh was FIRST with many marketing fiascos.  But not even in the
running for early history of binary measurements.

Grumpy Ol' Fred     		cisin at xenosoft.com

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