Files are required to store any information permanently, for later use. The same holds for data files also.
The data files are the files that store data pertaining to a specific application, for later use. The data files can be stored in the following two ways :
A text file stores the information in ASCII characters. In text files, each line of text is terminated or delimited with a special character named EOF known as End of Line character.
In text files, some internal translations take place when this EOF character is read or written.
A binary file is just a file that contains information in the same format in which the information is held in memory.
In binary file, there is no delimiter for a line. Also no translations occur in binary file. As a result, binary files are faster and easier for a program to read and write than are text files. As long as the file doesn't need to be read by people or need to be ported to a different type of system, binary files are the best way to store program information.
You can practice some C++ example programs, listed here, uses files: