Next task was to download lua source code which is readily available on internet as it is an open-source technology.I downloaded it and differntiated all the files into categories. It had .c and .h files.
for example

All the code was to be studied, not in whole but for having a basic understanding of what is in the files and what work they do.

Includes lua.h lauxlib.h lualib.h luaconf.h

Core lapi.c lcode.c ldebug.c ldo.c ldump.c lfunc.c lgc.c llex.c lmem.c lobject.c lopcodes.c lparser.c lstate.c lstring.c ltable.c ltm.c lundump.c lvm.c lzio.c

lapi.h lcode.h ldebug.h ldo.h lfunc.h lgc.h llex.h llimits.h lmem.h lobject.h lopcodes.h lparser.h lstate.h lstring.h ltable.h ltm.h lundump.h lvm.h lzio.h

Libraries lauxlib.c lbaselib.c ldblib.c liolib.c lmathlib.c loadlib.c loslib.c lstrlib.c ltablib.c linit.c

Interpreter lua.cAll

Compiler luac.c print.c