FORTRAN Reference Manual

Language Elements
FORTRAN Reference Manual—528615-001
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Initial Line
FORTRAN source lines contain the following elements:
Initial Line
A statement label, if present, begins anywhere in columns 1 through 5 (blanks are
ignored). Column 6 can be a blank or a zero (0). FORTRAN statements begin in
column 7.
Continuation Line
Continuation lines enable you to continue a statement beyond the limits of a physical
line. You designate a continuation line by placing any character, except a 0 or a blank,
in column 6. Begin the text of a continuation line in or after column 7. Following an
initial line, you can use up to 19 continuation lines to write one FORTRAN statement.
Comment Line
Designate comment lines by specifying the character C or an asterisk (*) in column 1.
The compiler treats all characters from column 2 to the end of the line as a comment.
You can place comment lines anywhere in a program. A line that contains all blanks is
a comment line. You can use blank lines to improve readability.
Column Meaning
1 If column 1 contains the letter “C” or an asterisk, the entire source line is a
comment.
If column 1 contains a question mark (?), the remainder of the record
contains compiler directives.
If column 1 contains a blank, the record is a continuation record or an
optionally labeled FORTRAN statement.
If column 1 contains any character other than a “C”, an asterisk, or a digit
from 0 through 9, FORTRAN reports a syntax error.
1 through 5 If column 1 does not contain a “C” or an asterisk, columns 1 through 5
contain a label. The label consists of any combination of the digits 0
through 9. Blanks, if present, are ignored. If columns 1 through 5 are
blank, the record does not contain a label.
6 If column 6 contains any character other than a zero (0) or a blank,
column 7 is the beginning of a continuation line. If column 6 is a zero or a
blank, column 7 is the beginning of a new FORTRAN statement.
7 through end
of line
If column 1 specifies a comment, columns 7 through the end of the line
are comment text.
If column 6 is a zero or a blank, column 7 is the beginning of a new
FORTRAN statement.
If column 6 is any character other than a zero or a blank, column 7 is the
beginning of a new FORTRAN statement.