Ok, Well hi! I'm learning to program in C# and I'm going to begin making game-save mod tools but before I even trying to make or release any thing I want need to get a better understanding of it. I know how to make the actual form with Open buttons, Save Buttons, Max All Stats, Text boxes, Numerical Up Downs etc and how to code them to work, like when I open, say for example a GTA IV gamesave with the tool It will search for the desired offset, read it and display it in a Textbox or Numerical Up Down, You can then modify it and press Save this then writes the text inside the textbox or numerical up down into the file. Correct? But I have just found out about this Checksum feature allot of games have, from what I understand is that a game that has a checksum will stop you from modifying it. So My question is that How would I know if the game has a checksum and how would I make the mod tool fix the checksum?