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  •  I don't have anywhere else to put this (none / 0)

    But I stumbled across a little factoid while browsing docs at IBM Research. The first IBM Executive Model A had 5 different possible character widths (which also doesn't mean that Models B, C or D couldn't have had more either).
    Ever since the invention of movable type, each letter in the alphabet had been given a unique width to make its appearance pleasing to the eye. The conventional fixedescapement typewriter required that all characters be of equal width. This squeezed large characters such as M and W and provided more than ample space for the thinner characters such as i and 1. To provide variable spacing for different letters, IBM's first proportional spacing typewriter used a rotary type of escapement mechanism of three separate escapement wheels designed to provide 2, 3, or 4 units of carriage motion [Fig. 2(a)]. Used in combinations, it was possible to obtain 2,3, 4, 5, or 6 units of carriage travel, which provided a wide range of possible character widths and a more pleasing quality of print. A subsequent design employing a multiple- pawl linear escapement [Fig. 2(b)] was first used in the Model A Executive and has remained basically unchanged for more than thirty years.

    Later the same document mentions that the Select Composer has 7 different character width possibilities

    Because providing for an unlimited variety of type widths was impractical, a compromise was established at seven different, selectable widths. Thus, all fonts were designed to fit a proportional system that provided escapement values of three through nine units with three pitch sizes of 1/72, 1/84, and 1/96 inch.
    Again, I'm just dumping this info here in case someone else can make use of it.

    by Gryn on Sun Sep 12, 2004 at 12:45:43 PM PDT

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    •  Great work (none / 0)

      thats really nice work. So do I understand it that on the executive the widest characters could only be 6 units and on the composer the widest characters could be 9 units?  Does that mean the widest characters on the composer are wider than on the executive?  Just want to make sure I am comparing apples to apples here.

      by Damon on Sun Sep 12, 2004 at 02:02:16 PM PDT

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      •  All signs point to maybe? (none / 0)

        It really seems like the units would correspond linearly, but I can't be sure yet.  It's possible that it's one of: linear, constant + linear, or something else.

        Given the contents of the second quote I'm pretty sure it's one of the first two (probably first).  Which means for a pitch size of 1/72 (inch?) you had a range of 1/24 - 1/8 (inch?).

        I'm really stretching on this however.  I'm open to better interpretations.

        by Gryn on Sun Sep 12, 2004 at 02:27:24 PM PDT

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        •  must be it (none / 0)

          On the composer at least thats how it works.  There are 3 unit settings.  On the narrowest there are 16 units per pica which is 96 units per inch.  Middle is 88 units per inch.  Widest is 72 units per inch.  

          On the exexutive there were no removable fonts (it was all a typepad) so I am guessing there was no ay to vary this setting at all.  And I certainly would guess that the executive's unit size was one of the composers but this could be wrong.  But to me the point is that we need to focus on getting the details for the composer then backtrack and see of the executive could also do it.  Basically anything the executive could do the composer can do as well.

          We have the character chart for the composer so we should be able to say exactly how long any given line of text would be if written on the composer right?  look at the may 4th memo in the line that starts out "1.  You are ordered" there are 453 units (assuming the default 3 units per space- there are 17 spaces so it could be off by a multiple of that)  453/72 = 6.29 inches.  The l vs 1 issue could also throw this off some.  

          The line below that "MAY,1972" should be 4.98 inches long using the same caveats.  

          Is there any way to determine from the PDF's how long those text lines are on the originals?

          by Damon on Sun Sep 12, 2004 at 02:54:33 PM PDT

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