Thread: read and write to file

hi, i was trying to write data to the end of a data file. i first read till the end of file and THEN tried write to the file. it compiles while,reads well..but wont write the data

this is my code

Code:

#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main(void){
	fstream myfile ("a.dat");
	string line;
	//read and go to end of file
	while (! myfile.eof() ){
		getline(myfile,line);
		cout<<line<<endl;
	}
	/*write to file*/
	char *line1="testing line1";	
	char *line2="testing line2";
	myfile.write(line1,15);
	myfile.write(line2,15);
}

hope some 1 can correct my error. thanx