Printing Terminals and Proportional Spacing

The IBM Executive typewriter allowed typed documents to somewhat resemble typeset text by varying the amount of space allocated to different letters. For example, with the Documentary font, a character could be from 2 to 5 units in width, where each unit was 1/32 of an inch. Other fonts, even when still typed at 6 lines to the inch, had a different basic unit; the Mid-Century font, for example, used a unit of 1/36 of an inch.

Using a crude dot-matrix font, the diagram below illustrates a unit system of this type:

and this keyboard chart includes typical character widths for such a unit system:

! 2 @ 5 # 3 $ 3 % 5 ¢ 3 & 4 * 3 ( 2 ) 2 _ 5 + 3
1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 3 0 3 - 3 = 3
  Q 4 W 5 E 4 R 4 T 4 Y 4 U 4 I 2 O 4 P 4 ¼ 5
  q 3 w 4 e 3 r 3 t 2 y 3 u 3 i 2 o 3 p 3 ½ 5
   A 4 S 3 D 4 F 4 G 4 H 4 J 3 K 4 L 4 : 2 " 3
   a 3 s 3 d 3 f 2 g 3 h 3 j 2 k 3 l 2 ; 2 ' 2
     Z 4 X 4 C 4 V 4 B 4 N 4 M 5         ? 3
     z 3 x 3 c 3 v 3 b 3 n 3 m 5 , 2 . 2 / 3

space = 2

2 fijlt I .,:;'!()
3 abcdeghknopqrsuvxyz JS 0123456789 "?#+-*/= 
4 w ABCDEFGHKLNOPQRTUVXYZ &
5 m WM @%_½¼

This is based on the unit system for Documentary at a unit size of 1/32", but may deviate from it for some of the special characters, my actual primary source being a font with the same spacing as Documentary for the letters which was used on a Friden Justowriter.

While we are on the topic of IBM trivia, and if we have wandered from punched card codes to line printers, another important input-output device, the IBM 2741 printing terminal, may also deserve some attention.

In the top two rows of this diagram, the two major families of 2741 arrangements are illustrated, first the arrangement of characters on the keyboard, and then the arrangement of characters on the typing element.

The arrangement at the top, the Correspondence arrangement, uses exactly the same elements as a standard office Selectric typewriter. The one in the middle is the PTTC/EBCD arrangement, which is designed so that the position of characters on the element leads to a code for the letters which has some relation to punched card codes and the EBCDIC internal code.

On the bottom is the keyboard arrangement, and arrangement of characters on the element, for another major family of devices using the IBM Selectric "golfball" element, but which was not made into a form of the 2741 terminal.

The charts of 2741 codes on the right shows the codes for the printing characters applicable to the Correspondence arrangement and then for the PTTC/EBCD arrangement; the relation between these is determined by matching characters in corresponding positions on the elements. The space and control characters always have the same codes.

Now that we have discussed the IBM Selectric Composer, here is a chart of its keyboard, including the widths of each of its characters in units, a unit being 1/72", 1/84", or 1/96" depending on the size of type being set, these sizes being indicated by red, yellow, and blue triangles upon the element respectively:

! 4 † 6 + 6 $ 6 % 8 / 4 & 8 * 6 ( 4 ) 4 _ 8 @ 8
1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 0 6 - 3 = 6
  Q 8 W 9 E 7 R 8 T 7 Y 8 U 8 I 4 O 8 P 6 ¼ 8
  q 6 w 8 e 5 r 4 t 4 y 6 u 6 i 3 o 6 p 6 ] 6
   A 8 S 6 D 8 F 7 G 8 H 8 J 5 K 8 L 7 ¾ 8 ½ 8
   a 5 s 4 d 6 f 4 g 5 h 6 j 3 k 6 l 3 ? 5 [ 5
     Z 7 X 8 C 7 V 8 B 7 N 8 M 9 ` 3 ' 3 : 4
     z 5 x 6 c 5 v 6 b 6 n 6 m 9 , 3 . 3 ; 3

space = 3

3 ijl  .,;`'-
4 ftrs  I  :!()/
5 acegz  J  [
6 bdhknpquvxy  PS  0123456789  ]+*=$†
7 BCEFLTZ
8 w  ADGHKNOQRUVXY &@%½¼¾ <em dash>
9 m  WM

where the underscore is filling the space that should contain a dash (I've seen pages that try to use &emdash; but that doesn't work), and I have cheated somewhat by using † or † to represent a dagger, which assumes you are viewing the page from within Microsoft Windows. The difference in width between colon and semicolon, and open and close square bracket, is intentional, and has to do with the desired amount of space after each character.

And, while we're on this topic, here is my attempt at a reconstruction of the unit system of the Mag Card Executive:

! 5 @ 5 # 5 $ 5 % 5 ¢ 5 & 5 * 5 ( 5 ) 5 _ 5 + 5
1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 5 0 5 - 5 = 5
  Q 7 W 7 E 6 R 7 T 7 Y 7 U 7 I 4 O 7 P 6 ¼ 5
  q 6 w 7 e 5 r 5 t 4 y 6 u 5 i 3 o 5 p 6 ½ 5
   A 7 S 6 D 7 F 6 G 7 H 7 J 5 K 7 L 6 : 5 " 5
   a 5 s 5 d 6 f 4 g 6 h 5 j 3 k 5 l 3 ; 5 ' 4
     Z 6 X 7 C 7 V 7 B 7 N 7 M 7         ? 5
     z 5 x 5 c 5 v 5 b 6 n 5 m 7 , 5 . 5 / 5

space = 5

3 ijl
4 ft  I  '
5 acehknorsuvxz J 0123456789 .,:;!?"@#$&¢()+-*/=_½¼
6 bdgpqy EFLPSZ
7 mw ABCDGHKMNOQRTUVWXY 

Although the Mag Card Executive is a rare machine, the same typefaces were used with the 96-character elements for the Model 50 Electronic Typewriter from IBM. This typewriter also typed in pica (1/10" monospaced) and elite (1/12" monospaced), and so I am confident that the unit size for this typewriter, and the Mag Card Executive, was 1/60", although at least one paper published in the IBM Journal of Research and Development claims a 1/72" unit for the Mag Card Executive. Comparing the spacing of this font to that of others, it can be seen that the spacing was designed for a font with a large x-height, the widths of the lower-case letters being larger in relation to those of the upper-case letters than in the other examples. Characters like @, %, and & were specifically designed to fit into the same relatively narrow space as digits to make it easier for typists to still put tables of numbers in uniform columns, even when some special symbols are used.

There may well be serious inaccuracies in the chart above, and someone out there with a Model 50 Electronic Typewriter, or a Model 65 or Model 85 may well be able to supply corrections. The forwards-pointing triangle on a Selectric Composer element indicated its spacing with its color; on a typewriter, a solid white triangle indicated pica, and a hollow triangle elite; proportional spacing was indicated by a circle, both on Model 50 elements and on those for the Mag Card Executive.

The 1/60" unit for proportional spacing of typed copy was, of course, also used on virtually all daisywheel printers that provided proportional spacing. A few even provided the option of printing small monospaced typing with letters 1/15" in width. Rather than being similar to the Mag Card Executive font, however, the proportionally-spaced fonts for some daisywheel printers tended to have small x-heights, a clear distinction between small and capital letters emphasizing that the font in use is proportionally-spaced.

Devoting all this space to unit systems and character widths, I might as well go "whole hog", and present this little cross-reference of some historical font metrics:

The large x-height of the typeface of the Mag Card Executive means that attempting to work it into the table above would not be possible without surrendering the table's neat appearance, as the relation of character widths for the same characters, even without including punctuation marks, where the differences are extreme (period and at-sign having the same width, where in other fonts the period is one of the narrowest characters, and the at-sign one of the widest), would cease to be monotonic.