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Annotation of 43BSDTahoe/new/help/src/f77/source, revision 1.1

1.1     ! root        1: .TI F77/SOURCE "Sep. 15, 1984"
        !             2: Format of Source Code Accepted by the f77 Compiler
        !             3: 
        !             4: F77 recognizes standard Fortran 77 source.  Lines with 'C' or '*' in column
        !             5: one or that are blank in columns 1-72 are comments.  Other lines have
        !             6: the following layout:
        !             7: 
        !             8: .nf
        !             9:          1-5:  statement number field
        !            10:            6:  continuation column (continuation if not blank or 0)
        !            11:         7-72:  statement body field
        !            12:        73-80:  sequence field
        !            13: .fi
        !            14: 
        !            15: Short lines are padded with blanks to column 72.
        !            16: 
        !            17: The rest of this help file describes non-standard extensions to the
        !            18: format and what they mean to f77.
        !            19: 
        !            20: F77 normally ignores case (except within Hollerith constants and
        !            21: character strings); thus a comment may also be indicated by a
        !            22: lower case 'c' in column one.
        !            23: 
        !            24: In character strings, the following backslash escapes are recognized:
        !            25: 
        !            26: .nf
        !            27:        \\n     newline character
        !            28:        \\t     tab character
        !            29:        \\b     backspace character
        !            30:        \\f     form feed character
        !            31:        \\0     null character
        !            32:        \\'     apostrophe (does not terminate string)
        !            33:        \\"     quotation mark (does not terminate string)
        !            34:        \\\\    \\
        !            35: .fi
        !            36: 
        !            37: F77 allows strings to be delimited by either apostrophes (') or double
        !            38: quotes (").  Whichever starts the string must also end the string.
        !            39: 
        !            40: Variable names may be up to 16 characters in length, and all 16 characters
        !            41: are significant.
        !            42: 
        !            43: Instead of using spaces to skip to column 7, a tab may be used.
        !            44: Continuation lines may be indicated by '&' in column one.  In both
        !            45: these cases, the statement body field starts with the character after
        !            46: the tab or '&' and continues to the last character of the source line
        !            47: whether before or after column 72.
        !            48: 
        !            49: This can effect the length of Holleriths and strings that are split across
        !            50: several lines.  This is rare, but is documented here for completeness.
        !            51: In the following example, there are no trailing blanks in the source
        !            52: file.  Tabs are used in the first format statement to skip to the
        !            53: statement body field, blanks are used in the second format statement:
        !            54: 
        !            55: .nf
        !            56:                print 100
        !            57:        c         tab between '100' and 'format'
        !            58:        100     format ( 'abcdefghijklmn
        !            59:             .opq')
        !            60: 
        !            61:              print 200
        !            62:        c         spaces between '200' and 'format'
        !            63:        200     format ( 'abcdefghijklmn
        !            64:             .opq')
        !            65:                end
        !            66: .fi
        !            67: 
        !            68: The printout is:
        !            69: 
        !            70: .nf
        !            71:        abcdefghijklmnopq
        !            72:        abcdefghijklmn                                        opq
        !            73: .fi
        !            74: 
        !            75: Because of the tab after '100' in the line containing format 100,
        !            76: that line is not padded with blanks;
        !            77: thus the 'opq' in the next line immediately follows
        !            78: the 'abcdefghijklmn' in the string in the format
        !            79: and also in the output.
        !            80: 
        !            81: Since blanks were used between '200' and 'format' in the line
        !            82: containing format 200,
        !            83: that line is padded with blanks out to column 72 so 'opq'
        !            84: is separated from 'abcdefghijklmn' by 40 blanks in the format and
        !            85: in the output.

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