HP HP-11C User Manual

Section 11: Programming Techniques 211
rewrite the subroutine’s steps eight times. What you also notice is
an increase in organization from using a subroutine. The program
has been broken down into its component parts. Each part, by
itself, is easier to read and understand than the unsectioned
program. Once the function of each part is understood, the
program can be read as a whole with better understanding. This
compartmentalization also simplifies error correction. Errors can
be more easily isolated and the corrections are less likely to have
adverse effects on other parts of the program.
(1ISG)With [RCL](()]
When looking for repeating patterns in your algorithms, it is also
good practice to look for sequential storage and recall, i.e., 1...
2 .. 3, etc. Such sequences may be incorporated into
subroutines via the ((i)]and ((i)) functions of the HP-11C.
This technique is effectively used in the Matrix Algebra program.
Routine “A” (lines 079 through 101) calculates the determinant of
the 3 X 3 matrix stored in Ry through R ;. Mathematically, the
determinant is calculated as:
Rs R¢ Ry R5(Rg XR3—RyXRy)
Rg Ry Ry|= —Rg(RgXR3—RyXR}))
R; R2 Rj +R7(Rg X Ry —Rg XR}).
Rearrange this to bring out the pattern:
~(RoXRyXR +RgXR3 xR, +R;XRgXR)
+R;XRyX R, + Ry XR3XR, +Re XR XR |
What results is not just the pattern R X R X R + but also the
sequential recall R; to R . These two features have been combined
into subroutine 9 (lines 001 to 009).
In this subroutine (Increment and Skip of Greater) is used to
increment the I-register (refer to page 128, Incrementing and
Decrementing the Index Register). Each call of the subroutine
increases the value stored in R| by 1 and recalls the value stored in
the register indicated by the value in R; ([RCL] [(i)]). Since the
fractional portion of the number in the I-register is always zero and

HP HP-11C Specifications

General

Brand	HP
Model	HP-11C
Category	Calculator
Language	English