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CHAPTER 7
PROGRAMMING GUIDELINES
This chapter
is
by
no
means intended as an exhaustive discussion
of
programming
techniques.
It
is
intended simply as a guideline, primarily for the novice program-
mer.
For
those who wish
to
go
more
deeply into the science
of
FORTRAN
program-
ming, a
number
of
references are listed in the bibliography
at
the end
of
the chapter.
The first section
of
this chapter deals with general guidelines applicable to program-
ming in any language. The second section lists suggestions for programming in
FORTRAN
specifically.
7.1
Program Development
The
recommended
approach
to
program
development
is
the so-called
'top-down'
method.
Essentially, this means defining a
program
in the broadest possible terms
initially,
and
then working down
through
a series
of
increasingly detailed steps
to
final code.
At
each level, debugging
is
performed
to
whatever extent possible before
going
to
the next level
of
refinement.
The
first step in this
approach
is
a
thorough
definition
of
the programming task.
7.1.1
Problem Definition
Before considering any actual programming,
one
must
understand
clearly
and
com-
pletely the problems involved.
For
example, a person
may
have
to
change the spark
plugs
on
his car. This
is
fine,
but
he will be better
prepared
if
he knows
that
inserting
the new plugs by
hand
first
and
using a plug wrench only for final tightening reduces
the possibility
of
stripping threads.
And
he will be better advised still
if
he
is
told
to
put
a trace
of
'anti-seize'
compound
on
the threads first
to
make
later removal
easier,
and
limit the chance
of
breaking a plug.
Similarly, knowing
that
a
program
must print
out
payroll statistics
is
insufficient.
Is
it to print out only employee names
and
net pay? Is it
to
show taxes withheld
(federal, social security, state, city,
ad
infinitum)? Should it show
other
deductions
for the
company's
stock plan, pension plan, credit union,
or
whatever? Should it
show the hours worked, splitting
out
overtime, shift differential, holiday,
or
vaca-
tion pay? Should it show accrued sick
or
vacation leave?
And
what
format
should be
used to display all this
information?
While the
progammer
need
not
state the specific algorithms
to
be used
at
this stage,
he at least needs
to
know in detail
what
input
the
program
will be receiving
and
in
what form,
and
exactly what
output
the
program
is expected to produce.
7.1.2 Program Documentation
Every
program
should have
good
documentionfrom
the beginning!
At
the earliest stage
of
program
development,
documentation
would normally be a
preliminary functional specification
of
the
program.
Ideally, this specification
should be reviewed by
one's
programming
peers for constructive criticism. Not only
will gaps be filled in,
but
this review creates
an
environment for exchanging theories
of
programming, for coworkers to familiarize themselves with each
other's
projects,
and
for developing a feeling
of
teamwork within a
programming
group.
7-1