Difference between .dat and .txt in c++

The extension of a file is a helper so that the operating system (or user) can choose the appropriate program to open it. The actual file contents do not matter. There are some conventions what extensions to use but there is nothing from keeping you to use any arbitrary extension for your files. For instance you can rename a .jar file to .zip-file and be able to open the file with pkunzip.

So for C++ the extension does not matter, but for you as a programmer it may give a hint of the file contents i.e. open it in text or binary mode.

Text files or .txt files are a bit hard to parse in programs and easy to read. whereas .dat is usually used to store data that is not just plain text.

Generally .txt files contains letters, characters and symbols which is readable.

.dat is binary text file in which data is not always printable on screen.