Manipulation of Files:

I am writing a large program (by my standards but certainly not by most) for school. Anyway, in both of my classes (that is the abstract data type, not school) I am manipulating files. Is there anyway that I can use a variable to connect the filestream to the directory file. I have tried using a string variable in declarations similar to the following:
ifstream inFstream;
inFstream.open(filename) //filename is a string

I get compile errors because it wants a constant value. Is there a workaround. I am hoping it is like dynamic arrays and there is a pretty simple answer.

Also, still on the topic of files. How can I goto a specific part of a file and manipulate it? The end of a file?

I learn best from examples but I'm definatatly a newbie at c++ so if you could tone down examples to something human it would be appreciated.

Thanks for any help you can provide:
retretret

if you are asking to open a file then this is how i do it..

----
char filename[12];
ifstream fin;

cout<<"enter file name : ";
cin.getline(filename,12,'\n');

fin.open(filename);
----

>>How can I goto a specific part of a file and manipulate it? The end of a file?

use eof command to detect the end-of- file
or the seekg comman

fin.seekg(30); --> goes to the byte# 30 in the file.