coming to j from k, j's c interface (undocumented as of j601) seems to lack the convenience i was used to. so i wrote j.h to look like k.h, but it's implementation is incomplete. i may revisit this when the c interface will be augmented and documented in the near future.
in the meantime, my code may be instructive for anyone wanting to interface to j from c. particularly, i avoid the use of LoadLibrary on windows by generating a lib file from j.dll
currently it lies here: http://ivorykite.com/apl/jx.html