By default, a
data transfer leaves the file positioned after the last record read
or written. This type of I/O is called advancing. Fortran 90 also
allows nonadvancing I/O, which positions the file just after the
last character read or written, without advancing to the next record.
It is character-oriented and can be used only with external files
opened for sequential access. It cannot be used with list-directed
or namelist-directed I/O.
To use nonadvancing
I/O, you must specify ADVANCE='NO' in the READ or WRITE statement. The example program in “File
access” uses nonadvancing I/O in the
first WRITE statement, which is reproduced here:
WRITE (6, FMT='(A)', ADVANCE='NO') &
' Enter number to insert in list: ' |
The effect of nonadvancing I/O on the WRITE statement is to suppress the newline character that
is normally output at the end of a record. This is the desired effect
in the example program: by using a nonadvancing WRITE statement, the user input to the READ statement stays on the same line as the prompt.
You
can get the same effect with the newline ($) edit descriptor, an HP Fortran extension that also
suppresses the carriage-return/linefeed sequence at the end of a
record; see “Newline
($) edit descriptor”.
For an example
program that illustrates nonadvancing I/O in a READ statement, see “Nonadvancing
I/O”. For more information about nonadvancing I/O
and the ADVANCE= specifier, see the READ and WRITE statements in Chapter 10.
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