Hi, I have this code in C for Flex/Lex, the only problem is that as I try to compile it it shows some errors and I dont know how to fix them.

letter [a-zA-Z]  
digit[0-9]
%%  
 {digit}+("E"("+"|"-")?{digit}+)? printf("\n%s\tis real number",yytext);  
 {digit}+"."{digit}+("E"("+"|"-")?{digit}+)? printf("\n%s\t is floating pt no ",yytext);  
 "if"|"else"|"int"|"char"|"scanf"|"printf"|"switch"|"return"|"struct"|"do"|"while"|"void"|"for"|"float" printf("\n%s\t is keywords",yytext);  
 "\a"|"\\n"|"\\b"|"\t"|"\\t"|"\b"|"\\a" printf("\n%s\tis Escape sequences",yytext);  
 {letter}({letter}|{digit})* printf("\n%s\tis identifier",yytext);  
 "&&"|"<"|">"|"<="|">="|"="|"+"|"-"|"?"|"*"|"/"|"%"|"&"|"||" printf("\n%s\toperator ",yytext);  
 "{"|"}"|"["|"]"|"("|")"|"#"|"'"|"."|"\""|"\\"|";"|"," printf("\n%s\t is a special character",yytext);  
 "%d"|"%s"|"%c"|"%f"|"%e" printf("\n%s\tis a format specifier",yytext);  
 %%  
 int yywrap()  
 {  
 return 1;  
 }  
 int main(int argc,char *argv[])  
 {  
 yyin=fopen(argv[1],"r");  
 yylex();  
 fclose(yyin);  
 return 0;  
 }

and the compiling problems I have are:

lexem.l: In function ‘yylex’:
lexem.l:4: error: ‘digit’ undeclared (first use in this function)
lexem.l:4: error: (Each undeclared identifier is reported only once
lexem.l:4: error: for each function it appears in.)
lexem.l:4: error: expected ‘;’ before ‘}’ token
lexem.l:4: error: invalid operands to binary | (have ‘char *’ and ‘char *’)
lexem.l:4: error: called object ‘"E"’ is not a function
lexem.l:4: error: expected expression before ‘{’ token
lexem.l:4: error: expected ‘:’ before ‘;’ token
lexem.l:5: error: expected ‘;’ before ‘}’ token
lexem.l:5: error: wrong type argument to unary plus
lexem.l:5: error: expected ‘;’ before ‘{’ token
lexem.l:6: error: invalid operands to binary | (have ‘char *’ and ‘char *’)
lexem.l:6: error: expected ‘;’ before ‘printf’
lexem.l:7: error: invalid operands to binary | (have ‘char *’ and ‘char *’)
lexem.l:7: error: expected ‘;’ before ‘printf’
lexem.l:8: error: ‘letter’ undeclared (first use in this function)
lexem.l:8: error: expected ‘;’ before ‘}’ token
lexem.l:8: error: expected ‘;’ before ‘}’ token
lexem.l:8: error: expected ‘)’ before ‘|’ token
lexem.l:9: error: invalid operands to binary | (have ‘char *’ and ‘char *’)
lexem.l:9: error: expected ‘;’ before ‘printf’
lexem.l:10: error: invalid operands to binary | (have ‘char *’ and ‘char *’)
lexem.l:10: error: expected ‘;’ before ‘printf’
lexem.l:11: error: invalid operands to binary | (have ‘char *’ and ‘char *’)
lexem.l:11: error: expected ‘;’ before ‘printf’
lexem.l:12: error: expected expression before ‘%’ token
lexem.l:23: error: stray ‘#’ in program

note that I am compiling using the "gcc -lfl lex.yy.c" command line, and thats where all the problems appear.

The syntax in this program you've written is completely wrong. It doesn't even appear to be real C code. What do you think the lines letter [a-zA-Z] and digit[0-9] do? What's with the two percent signs on the next line?

My apologies; the phrase "I have this code in C" threw me off and led me to beleive the OP was feeding the posted code directly into GCC.