Dat File Location

So i found this script on the internet

 StreamWriter writer = new StreamWriter("MyFile.dat");
 writer.WriteLine("Hello");
 writer.WriteLine("World");

I modified it to my script and added the using system.io; but where does it write to? I have the script running with no errors but i dont 100% know if it works because i can see where it saves to on a persons computer, i wanted to be able to choose the directory but if i cant well, that kind of sucks. Id imagine it being possible to choose but i dont 100% know yet.

READ BELOW AT THE COMMENTS

EDIT I posted an answer on a different post telling them to go to here so this is an example i use this in...

 using UnityEngine;
 using System.Collections;
 using System.IO;
 public class CharacterSelection : MonoBehaviour {
 
     public string CharacterName = "No Character Created!";
     public string psi;
     public string PVPTeam;
     public string Level;
     public string gold;
     public string EXP;
     public string LvlUP;
     public string angel;
     public string demon;
 
     public string button001;
 
     public int SelectCharacters = 1;
     public int CreateCharacters = 0;
     // Use this for initialization
     void Start () {
         PlayerController pc = (PlayerController)GetComponent("PlayerController");
 
         CharacterName = pc.Name;
         Level = pc.Level.ToString();
         PVPTeam = pc.PVPTEAM;
         psi = pc.PSI;
         gold = pc.Gold.ToString();
         EXP = pc.EXP.ToString();
         LvlUP = pc.LvlUP.ToString();
         angel = pc.isAngel.ToString();
         demon = pc.isDemon.ToString();
 
     }
     
     // Update is called once per frame
     void Update () {
         PlayerController pc = (PlayerController)GetComponent("PlayerController");
 
         if (SelectCharacters == 1)
         {
             button001 = "Create Character";
         }
         else
         {
             button001 = "Cancel";
         }
         ReadData();
         WriteData();
         
     }
 
     void OnGUI()
     {
         Select();
         Create();
 
         if (GUI.Button(new Rect(Screen.width - 200, Screen.height - 50, 150, 25), button001))
         {
             if (button001 == "Create Character")
             {
                 SelectCharacters = 0;
                 CreateCharacters = 1;
             }
             else
             {
                 SelectCharacters = 1;
                 CreateCharacters = 0;
             }
         }
         
     }
 
     public void Select()
     {
         if (SelectCharacters == 1)
         {
             GUI.Button(new Rect(10, 100, 10, 10), "<");
             GUI.Button(new Rect(250, 100, 10, 10), ">");
             if (GUI.Button(new Rect(30, 100, 200, 25), CharacterName))
             {
 
             }
         }
     }
     public void Create()
     {
         Login l = (Login)GetComponent("Login");
 
         if (CreateCharacters == 1)
         {
             GUI.Label(new Rect(10, 10, 200, 25), "Name: ");
             CharacterName = GUI.TextField(new Rect(50, 10, 125, 25), CharacterName);
             if (GUI.Button(new Rect(10, 40, 200, 25), "Create Character"))
             {
                 StreamWriter writer = new StreamWriter(Application.dataPath + "Users/" + l.username + CharacterName + ".dat");
                 writer.WriteLine(CharacterName);
 
                 SelectCharacters = 1;
                 CreateCharacters = 0;
             }
         }
     }
 
     public void ReadData()
     {
         PlayerController pc = (PlayerController)GetComponent("PlayerController");
         Login l = (Login)GetComponent("Login");
 
         StreamReader reader = new StreamReader(Application.dataPath + "Users/" + l.username + CharacterName + ".dat");
             string strAllFile = reader.ReadToEnd().Replace("\r\n", "\n").Replace("\n\r", "\n");
             string[] arrLines = strAllFile.Split(new char[] { '\n' });
             CharacterName = arrLines[0];
             Level = arrLines[1];
             EXP = arrLines[2];
             gold = arrLines[3];
             LvlUP = arrLines[4];
             psi = arrLines[5];
             PVPTeam = arrLines[6];
             angel = arrLines[7];
             demon = arrLines[8];
     }
 
     public void WriteData()
     {
         PlayerController pc = (PlayerController)GetComponent("PlayerController");
         Login l = (Login)GetComponent("Login");
 
         StreamWriter writer = new StreamWriter(Application.dataPath + "Users/" + l.username + CharacterName + ".dat");
             writer.WriteLine(pc.Name);
             writer.WriteLine(pc.Level);
             writer.WriteLine(pc.EXP);
             writer.WriteLine(pc.Gold);
             writer.WriteLine(pc.LvlUP);
             writer.WriteLine(pc.PSI);
             writer.WriteLine(pc.PVPTEAM);
             writer.WriteLine(pc.isAngel);
             writer.WriteLine(pc.isDemon);
 
     }
 }