Monospace

Monospace is an inheritance from the typewriter, where each key moved the carriage the same distance because it mechanically had to. It survived because two things turn out to need it: code, where columns have to line up and a misplaced character has to be countable, and tabular figures, where a column of numbers is unreadable if the digits are different widths.

Making it work is harder than it sounds. The letters that are naturally narrow have to be widened without looking stretched, and the naturally wide ones squeezed without looking crushed, which is why a good monospace has an i with long serifs and an m with tight joins. Faces drawn for code go further and pull the easily confused characters apart — a slashed or dotted zero, an l with a tail, a 1 with a base — because in code the difference between them is not a stylistic matter.