The difference between a data file and a program file is that?

A data file contains information of some kind. A program file is a piece of software that may allow you to read or create a certain type of data file, or play a game, or fix a problem, etc.

Microsoft Word is made up of program files, but My-document.doc is a data file that is read or created or edited by Microsoft Word.

Assassin's Creed is a computer game made up of program files, but the saved game files (which hold information about a particular run of the game so the player can restart where they left off) is a data file created by the game.

Diskeeper is a piece of software that re-orders the contents of a computer disk to make them more easily accessible by the computer (so the computer seems faster) - it is made up of program files, but doesn't create any usable data files, it is just a tool to manage your program and data files for greater efficiency.

DATA FILE: A collection of data records stored on a disk. Contrast with word processing file and graphics file.

PROGRAM FILE: Program Files is a folder in Microsoft Windows operating systems where applications that are not part of the operating system are installed by default.