What is file?

A series or sequence of bytes produced by a program that stored on disk and can normally be retrieved by a program for editing. A file has a starting and an end. An entry in the directory notifies the user that the file exists and an entry in the file allocation table of the disk tells the system how the file is physically distributed over the disk medium. In the narrower sense a file is for all time the product of a program (word processor, spreadsheet, etc.). In a more broad sense it is any coherent series of bytes with a beginning and an end and a name in the directory of the disk, for example, it can be a program file.