Fixed form, which dates back to the use of punch cards, meant that statement labels had to appear in the first five columns, column six was used for a continuation indicator, and statements appeared on lines 7-72. In Fortran 90 free source form means you are free to type comments and commands wherever you want. The comment statement follows the bang and continues to the end of the line. Comment statements are ignored by the compiler, but are very important for documenting your program. It is important to use comments frequently to clarify the procedures intended in a program.
Comments can be of great assistance to debugging and revising computer programs.
A line of Fortran 90 code can have a maximum of 132 characters. Only with character strings is the ampersand needed at the start of the next line.