www.delorie.com/gnu/docs/calc/calc_186.html search
GNU Emacs Calc 2.02 Manual

 [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ]

The cwidth function measures the width, in characters, of a composition. For example, cwidth(a + b)' is 5, and cwidth(a / b)' is 5 in normal mode, 1 in Big mode, and 11 in TeX mode (for {a \over b}'). The argument may involve the composition functions described in this section.
The cheight function measures the height of a composition. This is the total number of lines in the argument's printed form.
The functions cascent and cdescent measure the amount of the height that is above (and including) the baseline, or below the baseline, respectively. Thus cascent(x) + cdescent(x)' always equals cheight(x)'. For a one-line formula like a + b', cascent returns 1 and cdescent returns 0. For a / b' in Big mode, cascent returns 2 and cdescent returns 1. The only formula for which cascent will return zero is cvspace(0)' or equivalents.