# Source Code Useable for All Source Forms

To write source code that is useable for all source forms (free, fixed, or tab), follow these rules:

Blanks | Treat as significant (see Free Source Form).
Statement labels | Place in column positions 1 through 5 (or before the first tab character).
Statements | Start in column position 7 (or after the first tab character).
Comment indicator | Use only !. Place anywhere except in column position 6 (or immediately after the first tab character).
Continuation indicator | Use only &. Place in column position 73 of the initial line and each continuation line, and in column 6 of each continuation line (no tab character can precede the ampersand in column 6).

The following example is valid for all source forms:

    Column:
    12345678...
                                                                73
    _________________________________________________________________________

    ! Define the user function MY_SIN
          DOUBLE PRECISION FUNCTION MY_SIN(X)
            MY_SIN = X - X**3/FACTOR(3) + X**5/FACTOR(5)                    &
         &          - X**7/FACTOR(7)
          CONTAINS
            INTEGER FUNCTION FACTOR(N)
             FACTOR = 1
             DO 10 I = N, 1, -1
      10     FACTOR = FACTOR * I
            END FUNCTION FACTOR
          END FUNCTION MY_SIN

Parent topic: Source Forms