TrueType instructions are the means that we have for optimizing the rasterization of glyphs in a TrueType font. Unlike PostScript hints, they are not values of parameters or graphical zones but a genuine programming language. Furthermore, the view that font designers have of TrueType instructions is not very different from Freud's opinion of the unconscious: "a cave where repressed desires move around in the dark". Indeed, the sight of hundreds of lines of code of this type:
MIRP MIRP MIRP SRP1[ ] SRP2[ ] SLOOP[ ]
is enough to make anyone, not just a technophobe, break out in a cold sweat.
But is this cold sweat justified?
It is true that, unlike Adobe, Apple—which sparked the development of the TrueType instructions—has always been partial to "hard" notation in computer science, perhaps to highlight the contrast between the roles of Macintosh "user" (who communicates with his machine through menus and dialog boxes) and "programmer" (who stumbled into assembly language as a child).
We might have envisioned a high-level language that, when compiled, would produce the assembly code for the instructions of today; after all, that is precisely what Knuth did with METAFONT (see Appendix F). This high-level language does not yet exist and, no doubt, never will. Nonetheless, various tools have been created to make up for this deficiency: FontLab offers a simplified version of instructions with a graphical interface; Visual TrueType, by ...