2. the "\\" for "\" seems to work (does not report error. "\." now complain, but not if I enter '.', as if \ was only an escape for \ except when followed by n as in \n.
Uhmm ... and what escape is \. supposed to be? You are confusing C escapes with regular expressions I think.
3. The error I am reported now is that "isascii" us an unknopwn symbol.
Did you include <ctype.h> ??
Test your code with gcc please. If it compiles under gcc and then fails under tcc, then this is the proper list. If it won't compile under gcc, then perhaps stackoverflow would be a better place for help.