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FORTRAN-SO Programming Guidelines
When calculating a value for use in a
DO
loop, be sure the value
is
computed
before
the loop
is
entered. Otherwise, the
program
could
compute
the
value again for each
iteration
of
the loop. Consider the following
short
Examples:
C EXAMPLE
OF
RECOMPUTED CONSTANT
INTEGER*1
R
DO
25
R =
1,60
X = (2217)*(r* *2)
WRITE (4)
X,
R
25
CONTINUE
C SAME
EXAMPLE WITH PRECOMPUTED
CONSTANT
INTEGER*1 R
PI
=
2217
DO
25 R =
1,60
X =
PI*(R**2)
WRITE
(4)
X,
R
25
CONTINUE
In the first case, the value
'22/7'
would have to be
computed
60 times!
7.2.5 Reminders
We've
already mentioned the use
of
comments,
good
mnemonic names,
and
blanks
to improve
program
readability
and
understandability. We've also mentioned
debugging aids available in the
FORTRAN
language (such as the
PAUSE,
STOP,
and
WRITE
or
PRINT
statements). In addition, the
programmer
should explore
other
debugging tools
that
might be available in his system environment, such as the
DEBUG
command
in Intel's ISIS-II
or
Intel's in-circuit
emulator
family, which in-
cludes
ICE-80
and
ICE-85 for the 8080
and
8085 microprocessors.
7.3 References
The
following list suggests material for further reading. Some
of
the material, like
the books by Ledgard
and
McCracken
or
the article by Ogdin,
is
essentially tutorial.
Bear in mind
that
all
of
this material was written before
FORTRAN
77
~as
specified
and
FORTRAN
'limitations'
discussed in these works may
no
longer be a problem
in the new version.
Dahl,
0.1.,
Dijkstra,
E.W.
and
Hoare,
C.A.R.,
Structured Programming,
Academic Press, New York, 1972.
Dijkstra,
Edgar
W.,
'GO
TO
Statement Considered
Harmful,'
Communications
of
the A CM, Vol. 15, No.
10,
Oct. 1972.
Henderson,
P.,
and
Snowdon,
R.,
'An
Experiment in Structured
Programming,'
BIT
12, 1972.
Hilburn,
1.L.,
and
lulich,
P.M.,
Microcomputers/Microprocessors: Hardware,
Software,
and
Applications, Prentice-Hall, Inc., 1976.
Knuth,
Donald
E.,
The
Art
of
Computer
Programming, Vol.
1,
Fundamental
Algorithms, Addison-Wesley, Reading, Mass., 1968.
Ledgard,
Henry
F.,
Programming Pro verbs
for
FORTRAN
Programmers, Hayden,
Rochelle
Park,
N.l.,
1975. .
7-5