(HP-65) Percent Functions

[Dave Britten]

Strangely, I couldn't find a program like this in the Standard Pac or any of the add-on application pacs, but this program adds the basic % and Δ% functions of other HP calculators. There was plenty of memory left over to also include versions of these functions that work directly with D.MMSS inputs.

EDIT: I've incorporated Bob's suggestion below to add a %T (percent-of-total) function to the unused E key.

Recommended Key Labels

A: %
B: Δ%
C: D.MS%
D: D.MSΔ%
E: %T

Usage

The % and D.MS% functions calculate x percent of y, and place the result in x while leaving y, z, and t unchanged (R9 is used to preserve t). The D.MS% function expects y to be in D.MMSS format, and will return the result in the same format. You can then follow these functions with + or - (or f/f^-1 D.MS+) to calculate x percent increase/decrease in y.

The Δ% and D.MSΔ% functions calculate the percent change from a starting value in y to a final value in x. D.MSΔ% expects both x and y to be in D.MMSS format. Both functions consume the values in x and y, with the result returned in x, and t being copied when the stack drops.

The %T function calculates what percentage of y is equal to x. Like the % and D.MS% functions, it leaves y, z, and t unchanged.

Code:

LBL     23
A       11
g RUp   35 09
STO     33
9       09
g RDown 35 08
EEX     43
2       02
/       81
g x><y  35 07
*       71
g LSTx  35 00
g x><y  35 07
RCL     34
9       09
g RDown 35 08
RTN     24
LBL     23
B       12
g x><y  35 07
LBL     23
1       01
-       51
g LSTx  35 00
/       81
EEX     43
2       02
*       71
RTN     24
LBL     23
C       13
g x><y  35 07
f-1     32
D.MS    03
g x><y  35 07
A       11
f       31
D.MS    03
g x><y  35 07
f       31
D.MS    03
g x><y  35 07
RTN     24
LBL     23
D       14
f-1     32
D.MS    03
g x><y  35 07
f-1     32
D.MS    03
GTO     22
1       01
LBL     23
E       15
g       35
1/x     04
A       11
g       35
1/x     04
RTN     24