Question

how to read and write in files in c++?

Answer 1

Use fstream class...
For text files,
fstream f("example.txt",ios::in|ios::out);
This file now you can both write and read if you want to only read then use only ios::in and remove the ios::out.
just use the normal input like,
int g; f>>g; for input and f<<"This is writing\n";for output.

Answer 2

that is to say use f>> and f<< instead of cin and cout?

in PASCAL we just
assign(input,'input.txt');reset(input);
assign(output,'output.txt');rewrite(output);

and we have to close(input);close(output); at the end of a program.
so do i need to close files in c++?

Answer 3

yeah you need to close . just use f.close();
f<< and f>> are just simple input, output If you want better methods of input there is a getline function eg.
char ch[30];
f.getline(ch,30,'\n');
This basically reads a max of 30 chars and ends if it reaches a '\n'character. There is a put function for output but that is basically of no use so f<< is pretty good.