/in/foo.c: In function 'main':
/in/foo.c:23:2: warning: implicit declaration of function 'Output' [-Wimplicit-function-declaration]
  Output(c,nc);
  ^~~~~~
/tmp/ccFJLUAe.o: In function `main':
foo.c:(.text.startup+0xba): undefined reference to `Output'
collect2: error: ld returned 1 exit status