If you literally want to morph text in C then the only way that I can think of is to do it by hand in the Spline Modeller. You need to adjust the cross-sections by hand, you can't import a new outline, so it's not very easy. Otherwise it needs to be faked in some way, as nomuse suggests. If there are common letters to your two words then you might simply move them around, introducing new letters by changing their size or visibility. But if you're planning doing a lot of this then a deicated program will be the best way.