implicit declaration error

[Fractal A.]

Hi,

I'm compiling some files flex & bison from the O'Reilly site using bison 1.28
in cygwin.  

I'm getting an error implicit declaration of int free(...) & int yylex(...).  

What does the error mean?  How do I fix it?  Thanks in advance for your help. 
:)

>flex -t ch1-05.l > ch1-05.l.cxx

>bison -t -v -d ch1-05.y -o ch1-05.y.tab.c

>g++ -Wall -gstabs -DFLEX_DEBUG ch1-05.l.cxx -lfl -o a.exe
ch1-05.l:453: warning: `void yyunput(int, char *)' defined but not used

>g++ -Wall -c -gstabs ch1-05.l.cxx
ch1-05.l:453: warning: `void yyunput(int, char *)' defined but not used

>g++ -Wall -c -gstabs ch1-05.y.tab.c
/usr/share/bison.simple: In function `int yyparse()':
/usr/share/bison.simple:361: implicit declaration of function `int free(...)'
/usr/share/bison.simple:432: implicit declaration of function `int yylex(...)'

>g++ -Wall -gstabs ch1-05.y.tab.o ch1-05.l.o -lfl -o b.exe
G__~1: ch1-05.y.tab.o: No such file or directory

>rm ch1-05.l.* ch1-05.y.*


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Fractal A.                    address@hidden

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