Opening and closing files

Could something like this be done in a the same program. Im trying to figure out why I cannot open a file I just wrote to. If it cannot be done then problem found. Or is this a big NO NO?

Code:

inData.open("qwert.dat");
outData.open("asdfg.dat");

/////////////////
Do some stuff
/////////////////

inData.close();
outData.close();

inData.open("asdfg.dat");        //open the file I just wrote and closed

/////////////////
Do some stuff
/////////////////

inData.close();                         //close the file again

/////////////////
Do some stuff
/////////////////

outData.open("asdfg.dat");     //doing this blanks the file

/////////////////
Do some stuff
/////////////////

outData.close();

when you open a file to write to it will put the "cursor" at the beginig of the file.
so if you want to add to the end of the file you need to append the file, so that it will add to the bottom of the file rather then the top
alas, i only have partial commands for that.
hope someone else can provide the syntax for ya

http://www.cprogramming.com/tutorial/lesson10.html
http://www.cplusplus.com/ref/iostream/fstream/open.html

use ios::app it will do the job.