c++ sqlbindparameter

here declarations variables:

string strfirstname;
string strlastname;
string straddress;
string strcity;
string strstate;
double dblsalary;
string strgender;
int intage;

...do "cin" statements data...

retcode = sqlprepare(statementhandle, (sqlchar *)"insert worker ([firstname], [lastname], [address], [city], [state], [salary], [gender],[age]) values (?,?,?,?,?,?,?,?)", sql_nts);

retcode = sqlbindparameter(statementhandle, 1, sql_param_input, sql_c_char, sql_longvarchar, 50, 0 &strfirstname,0, null);

retcode = sqlbindparameter(statementhandle, 2, sql_param_input, sql_c_char, sql_longvarchar, 50, 0, &strlastname,0, null);

retcode = sqlbindparameter(statementhandle, 3, sql_param_input, sql_c_char, sql_longvarchar, 30, 0, &straddress,0, null);

retcode = sqlbindparameter(statementhandle, 4, sql_param_input, sql_c_char, sql_longvarchar, 30, 0, &strcity,0, null);

retcode = sqlbindparameter(statementhandle, 5, sql_param_input, sql_c_char, sql_longvarchar, 3, 0, &strstate,0, null);

retcode = sqlbindparameter(statementhandle, 6, sql_param_input, sql_c_double, sql_double, 0, 0, &dblsalary,0, null);

retcode = sqlbindparameter(statementhandle, 7, sql_param_input, sql_c_char, sql_longvarchar, 2, 0, &strgender,0, null);

retcode = sqlbindparameter(statementhandle, 8, sql_param_input, sql_c_long, sql_integer, 0, 0, &intage,0, null);

retcode = sqlexecute(statementhandle);

the int double work glorious stored table...but i can't figure out strings store...