This might help you understand it: http://code.kx.com/wiki/Cookbook/InterfacingWithC

Once you understand the underlying data structure, a lot of k's design decisions make sense. I am using the k.h file from k4 as almost the sole guide to recreating a toy k5 (http://kparc.com/k.txt) interpreter in C.

Perhaps you should start with a manual instead of C headers: http://web.archive.org/web/20041022042401/http://www.kx.com/...