The format part is where you can specify more precisely the format of the data that you expect. For instance, if you have a format specifier like: read (25,"(2X, 2I5, F7.3, A)") Here, the "2X", refers to 2 spaces, the "2I5", refers to 2 integers that are 5 digits, "F7.3", refers to a decimal value which has a total length of 7, with three digits after the decimal. The "A" refers to a character. You can check out some more of these