Re: Will IBM 360 Floppies work in Apple ][ Drives?

["Michael J. Mahon" <mjmahon@aol.com>]

Paul Schlyter wrote:
> In article <45dce030$0$20288$9b4e6d93@newsspool3.arcor-online.net>,
> Linards Ticmanis  <ticmanis@gmx.de> wrote:
>
>
> > David Empson wrote:
> >
> >
> > > I used the standard IBM 8" SSSD floppy disks on a CP/M system in the mid
> > > 80s. If memory serves, it had 40 tracks, 32 sectors per track, 128 bytes
> > > per sector, which would be 160 KB.
> >
> > I seem to remember that it was 77 tracks of 26 sectors (or some other
> > fairly odd numbers). Never had one, but CP/M has some built in tables
> > for these. That's were those ugly 128 byte records come from that almost
> > everybody else had to block/deblock in their BIOS, wasting precious space.
> >
> > Just looked into wikipedia: it was really 77x26x128. Equivalent to 2002
> > punch cards (2000 was a common box size for those, it seems).
>
>
> Since 77*26 = 2002, this corresponds to 128 bytes per punch card.  But
> wasn't the standard punch card 80 columns rather than 128 columns?
> OK, each column had 12 punch locations instead of 8 - but if we
> consider each punch location one but, that's still isn't enough for
> 128 bytes, only for 120 bytes.
>
> The punched cards were used well before the computer age, actually as
> early as 1725!  The IBM standard 80-column punch card originated in 1928.

Right, and it's 80-column width was designed to approximate the needs
for unit record accounting.  (Remington Rand came to the slightly larger
conclusion that 90 characters would be appropriate.)

The original design was decidedly decimally oriented, and the extension
to alphanumerics through the "zone" punches was a later addition.

When computers came on the scene, cards were adapted as input/output
media, and eventually generalized to first "row binary" (with 24 words
of 36 bits each punched two words to a row--and the last 8 columns left
for a sequence number), and later "column binary".

The 12-row x 72- or 80-column format was never a particularly smooth
fit with the power-of-two world popularized by the System/360, which
led to the introduction (with the System/3) of a smaller punched card
with small round holes (shades of Remington Rand!) with 96 characters
per card, arranged in three rows of 32 characters.  After a brief
flurry, they faded away, as punched cards practically disappeared.

At first, a few terminals showed up in "keypunch rooms", then more
terminals and fewer keypunches, then, within a couple of years, you
could only find a keypunch in the corner of a back room!

Although there were a few earlier attempts (Datapoint, for example)
to replace keypunches with "direct-to-tape" keyboarding, what finally
did the punched card in was the multiplexing of *lots* of terminals
into systems running on-line editors.

Although "glass TTY" editing is certainly much more effective than
keypunch editing, I occasionally reminisce about "thumb edits" on
keypunch machines, in which one could insert and delete characters
while otherwise duplicating a card.  ;-)  And it was great fun
punching "drum" cards for tabs, shifts, and auto-dups!  ;-)

-michael

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