HP HP-11C

Section 11: Programming Techniques 207
leaving the details out. The necessary details will be filled in later
as programming language, space, and personal preference dictate.
For now, all we are trying to accomplish is to lay down the
foundations of the solution. In the case at hand, we might choose to
solve the problem using the quadratic equation, namely:
. —b +\/b% —4ac
2a
With this equation to guide us, our initial algorithm might look like
this:
Find b2 — 4ac.
If the difference is positive, find
—b +\/b% —4ac
2a
If
the
difference
is
negative,
find
——;b
and
£_|£2“_:_:4_ac_|
a
a
In the case where b? — 4ac is positive, the solution is in the form of
two real roots. When the difference is negative, the solution is in
the form of two complex numbers. Note that none of the above
statements define actual program steps. What is defined is the
sequence of events required to arrive at the solution.
Refinement of the basic algorithm will bring out repeating patterns
and condensable sequences that suggest the actual program steps
that will ultimately be used. The revision process will also help to
keep your programming objectives in mind. One such refinement
might be:
Using the hypothetical registers R 4, R g, and R do the following:
1. Takethe negative of b and divide it by twice a.
2. StorethisresultinR 4.
3. Square b, subtract four a times ¢ from it and store the result
in R B-
4. Take the square root of the absolute value of Rg and divide it
by twice a.