Tabs in the Source

f90 allows the tab character in fixed-form source and in free-form source. Standard Fortran 90 does not allow tabs.

The tab character is not converted to a blank, so the visual placement of tabbed statements depends on the utility you use to edit or display text.

Fixed-Form Source

• For a tab in column one:

  If the next character is a nonzero digit, then the current line is a continuation line; otherwise, the current line is an initial line.

• A tab cannot precede a statement label.

• A tab after column one is treated by f90 the same as a blank character, except in literal strings.

Free-Form Source

f90 treats a tab and a blank character as equivalent, except in literal strings.