All control values have an identification number, as well as a comment that provides information about the type of glyph or feature to which it applies. A typical entry in the ‘cvt’ table looks like this:
66: 192 0xa41
where
· The control value number (here, 66) is the sequential number identifying the entry in the table. Links, anchors, and strokes can refer to this number. Some of these are reserved. For example, line 36 always is the italic size run.
· A colon separates the first two numbers.
· A control value (here, 192) gives the dominant length or width of a feature, measured in font units (F-units) scaled to the ppem height of the device grid.
Any feature that needs to be controlled can be assigned a value and reference number in the ‘cvt’ table. Typically, a ‘cvt’ table includes entries for common heights (for example, baseline, cap height, and x-height), representative side-bearing points, common uppercase and lowercase stem widths (both X and Y directions), uppercase and lowercase serif thickness and length, and any italic angle.