UNFORMATTED or BINARY I/O

The mode of I/O discussed so far in this section is called FORMATTED or ASCII because the conversion action of the * or FORMAT statement means that the external data form is text (on most machines text uses ASCII character codes). There is a second mode called UNFORMATTED or BINARY. The forms of the READ and WRITE statements are exactly the same except that there is no format reference. e.g.

READ(INPUT,END=200,ERR=250) ZZZ

The data is transmitted as a set of bit patterns - the internal form of the data within the program is identical to the external form. This is a much more compact way of storing data but binary files cannot be listed - they can only be read by other FORTRAN programs.