Open Watcom FORTRAN 77 Language Reference

Language Reference
1.3 Source Program Format
Open Watcom FORTRAN 77 supports one source program format. A FORTRAN program is composed of
lines. There are three types of lines; the comment line, the initial line, and the continuation line.
1.3.1 Comment Line
Comment lines are denoted by placing a "C" or "*" in column one of the line. Open Watcom FORTRAN
77 also allows the use of a lowercase "c" as a comment indicator. Blank lines are treated as comment lines.
Comment lines may be placed anywhere in the program source (i.e., they may appear before a FORTRAN
statement, they may be intermingled with continuation lines, or they may appear after a statement). There
is no restriction on the number of comment lines. Comment lines may contain any characters from the
processor character set.
Open Watcom FORTRAN 77 allows end-of-line comments. If a "!" character appears in column 1 or
anywhere in the statement portion of a source line, the remainder of that line is treated as a comment unless
the "!" appears inside quotation marks or in column 6.
1.3.2 Debug Line (Extension)
Debug lines are denoted by placing a "D" or "d" in column one of the line. Debug lines contain
FORTRAN statements. There is no restriction on the number of debug lines. Normally, the FORTRAN
statements on debug lines are ignored by the compiler. See the User’s Guide for information on activating
debug statements.
1.3.3 Initial Line
An initial line is the first line of a FORTRAN statement. Column 6 of this line must be blank or contain the
digit "0". A comment line can never be an initial line. Columns 1 through 5 of an initial line may contain a
statement label. Statement labels are composed entirely of digits. The statement label may be thought of
as an integral number and, as such, leading 0 digits are not significant. For example, the label composed of
the digits "00123" is the same as the label "123". The same label may not identify more than one statement
in a program unit. A program unit is a series of comment lines and FORTRAN statements ending in an
END statement. The body of the FORTRAN statement is entered starting in column 7 and stopping at
column 72. Column 73 and on is called the sequence field and is ignored by the compiler.
1.3.4 Continuation Line
A statement may be continued on a new line. A continuation character is placed in column 6. The
continuation character may not be a blank character or a "0" character. FORTRAN 77 requires that the
continuation character be selected from the FORTRAN character set but Open Watcom FORTRAN 77
allows any character from the processor’s character set. The statement number field must be blank. The
previous statement is continued on the new line, starting in column 7 and continuing to column 72. Under
the control of a compiler option, Open Watcom FORTRAN 77 permits the source statement to extend to
column 132.
4 Source Program Format