This question is so, so very common.

The best way to fix this is…

…to pass the filename as argument to your program. Then tell your IDE to give the full file path as argument when it runs your program. You can do this in all IDEs. In MSVS, it’s at Project → Settings → Debug → Program Arguments (last I checked).

quux.cpp

int main( int argc, char ** argv )
{
  if (argc != 2)
  {
    std::cerr << "usage:n"
      "quux FILENAMEn";
    return 1;
  }

  std::ifstream f( argv[1] );
  ...
}

Another (less awesome) way to fix it…

…is to hard-code the full path. This kind of solution keeps professors and TAs up at night having to modify your program to simply work.

  std::ifstream f( "C:/Users/Jhgg/Programming/AssignmentN/hashText1.txt" );

Rationale

In order to be clear, “less awesome” is programmer-speak for “it works, but don’t do this if you value a reputation as someone who knows what they are doing”. I mention it because it is a quick-n-easy kludge for dealing with something before you put in the proper code to do it right.

The “best way” is yet more programmer-speak to say “do it this way because <good reasons>”.

_{^{Those reasons may very well be opinion, but there are actual reasons involved, not just ego.}}

Reason 1 • It is expected behavior

Let us take the GNU Image Manipulation Program as an example. GIMP is a program that operates on image files. Load ’em, edit ’em, save ’em.

Notice how when you are scrolling around using your file explorer and right-click on an image, one of the options is to “Open this file with GIMP”? How does your file explorer actually do that?

Easy. It calls the gimp executable with the image filename as argument.

You can even drag an image file and drop it on the GIMP executable and it will open GIMP with the image already loaded!

From the command shell prompt, you can type gimp cats.jpg and it will start GIMP and load “cats.jpg” ready for editing.

Amazing!

Reason 2 • It makes life easier for everyone

By moving the name of the file to open into the user’s hands, your program becomes infinitely more useful.

• You no longer have to edit the source code and recompile to open a different file.
• You do not have to copy data to a specific file name.
• You don’t have to worry if your directory structure changes.
• You can run your program on a different computer without having to make your users create a user account just for your program!
• Testing your program with different inputs becomes simpler (just give it a different file)!
• …there’s more…

The point is, it moves control into the hands of both you (the programmer) and other users of your program (such as the TA grading your assignment, who will grade you much more nicely when your program is Easy To Use™).

Reason 3 • People won’t despise your program (or you)

This is kind of an et sequitur bit, but when people download software that is difficult to use… they toss it. They tell all their friends and internet acquaintances. They’ll send you hate email about how much time they wasted on your program. Your program won’t just be forgotten, it’ll burn in hell. And any other software you write will have the soot stains on it, regardless of quality.

Reason 4 • It is super-mega-ultra-über-easy

Seriously. How hard is it to type:

if (argc != 2) return usage();
std::ifstream f( argv[1] );`.

Then just use your file explorer to find the input file, Ctrl–C, then open your IDE’s “run program with arguments” option and Ctrl–V.

Done! Program runs from the IDE easy-peasy!

Hopefully this elucidates things a bit. Programming is often about being picky about little things that have big impact and taking the time to set things up to make life easier later.

^{/end rando lecture}