I am using MS Visual C++ 6.0. Can anyone tell me why I am getting these errors within my header file(these are only a few of the errors):

rror C2146: syntax error : missing ';' before identifier 'bkIsbn'
c:\program files\microsoft visual studio\myprojects\book\book.h(13) : error C2501: 'string' : missing storage-class or type specifiers
c:\program files\microsoft visual studio\myprojects\book\book.h(13) : error C2501: 'bkIsbn' : missing storage-class or type specifiers
c:\program files\microsoft visual studio\myprojects\book\book.h(14) : error C2146: syntax error : missing ';' before identifier 'bkTitle'
c:\program files\microsoft visual studio\myprojects\book\book.h(14) : error C2501: 'string' : missing storage-class or type specifiers
c:\program files\microsoft visual studio\myprojects\book\book.h(14) : error C2501: 'bkTitle' : missing storage-class or type specifiers
c:\program files\microsoft visual studio\myprojects\book\book.h(15) : error C2146: syntax error : missing ';' before identifier 'bkAuthor'
c:\program files\microsoft visual studio\myprojects\book\book.h(15) : error C2501: 'string' : missing storage-class or type specifiers
c:\program files\microsoft visual studio\myprojects\book\book.h(15) : error C2501: 'bkAuthor' : missing storage-class or type specifiers
c:\program files\microsoft visual studio\myprojects\book\book.h(16) : error C2146: syntax error : missing ';' before identifier 'bkPublisher'

Here is what I have in my header file:

#ifndef _BOOK
#define _BOOK

class Book
{
private:
string bkIsbn;
string bkTitle;
string bkAuthor;
string bkPublisher;
int bkPubYr;
int bkNumInStock;
int counter;
double bkPrice;

public:
Book(string, string, string, string, int, double, int);
~Book();
};

#endif