book, page 270, defines this mode.)
That means writing unmagnified font files with a resolution of
2601.72 dots per inch (dpi); that's 36 pixels per point. (One
point is 1/72.27 of an inch.) Proof mode does not produce a
TFM file.
The purpose of is to make fonts. For æsthetically pleasing PK bitmaps, the correct device mode must be selected.
An obstacle to beware of is that plain uses
proof mode by default.
(The book, page 270, defines this mode.)
That means writing unmagnified font files with a resolution of
2601.72 dots per inch (dpi); that's 36 pixels per point. (One
point is 1/72.27 of an inch.) Proof mode does not produce a
TFM file.
What good is proof mode, and why is it the default? Proofs are blown up copies of characters used by font designers to judge whether they like the results of their work. Naturally, proofs come first, and normal sized character production later — if you're a font designer.
So there are two clues that proof mode is on: font files with extensions like `.2602gf' (or on MS-DOS, `.260'), and the `failure' to produce any TFM file.
On some systems, such as X11, a third clue is that the proof font may be drawn on the screen — it's so large, you can't miss it!