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6-22
scanner
encounters
a
dollarsign
at
the
end
of
a
format
specification list,
format
con;.
trol
terminates
without
positioning
the
file
to
the beginning
of
the
next
record.
The
donar
sign .edit
descriptor
has
no
effect
on
direct~accessfil¢s.
Example:
PAINT 25, PNAME
25 FORMAT (A20, $)
6.4.4 List·Directed Formatting
I
List-directed
formatting
is
indicated by specifying
an
asterisk (*) in the
format
specifier
of
a
data-transfer
110
statement's
control
list (section 6.3.1.1.2).
It
allows
free
form
input
and
output,
which
is
especially helpful
if
the
110
device
is
a console
terminal. No
FORMAT
statement
is
required as all necessary
formatting
is
done
for
the
programmer.
A list-formatted file consists
of
a string
of
values
and
value
separators.
Each
value
is
either a
constant,
a null value, or a
constant
or null value prefixed by a repeat
specification in the form:
r*c
r*
The
first form
is
equivalent
to
'r'
successive
appearances
of
the
constant
'c;'
the se-
cond
is
equivalent
to
'r'
null values. A null value
can
also be specified as
no
characters
between value
separators
or
no
characters
preceding the first value
separator
in a record.
The
null value
is
not
produced
by list-directed
output.
Value
separators
can
be a
comma,
slash,
or
one
or
more
blanks
between
constants
or
following the last
constant
in a record.
The
slash
separator
is
not
produced
on
out-
put.
When
encountered
during list-directed
input,
it terminates execution
of
the in-
put
statement
after
assignment
of
the previous value.
If
the
110
list
contains
addi-
tional items, they
are
effectively assigned null values.
Any sequence
of
blanks
is
treated as a single
blank
except when
it
appears
within a
character
constant.
An
end-of-record
has the same effect as a
blank.
6.4.4.1 List-Directed
Input
Input
forms acceptable
to
format
specifications for a given type
are
acceptable for
list-directed
formatting
with a few exceptions. Blanks
are
never
treated
as zeros,
and
may not be
embedded
in
constants
(except
character
constants).
An input list item
of
type real
is
assumed
to
have
no
fractional
part
in
its
input
form
unless a decimal
point
appears
within the field. An
input
list item
of
type logical
must not include either slashes
or
commas
in its input
form.
An
input
list item
of
type
character
consists, in its
input
form,
of
a
nonempty
string
of
characters enclosed in
apostrophes.
Character
constants
can be
continued
from
the end
of
one
record
to
the beginning
of
the next.
Though
the
end
of
a record nor-
mally has the effect
of
a
blank
in list-directed
formatting,
a
blank
is
not inserted
into
the
character
constant
in this case.
Character
constants
are
transferred
left-justified
and
are
truncated
on
the right
if
their length exceeds the width
of
the
input
list item.
A null value has
no
effect
on
a
corresponding
input
list item.
The
item retains its
previous value
or
remains
undefined,
depending
on
its
status
before
the null value
was
encountered.
FORTRAN-SO