HP 20S and HP 21S: RPN Arithmetic Simulator
This program
will allow the user to simulate RPN (Reverse Polish Notation) for five
arithmetic functions: addition, subtraction, multiplication, division, and exponentiation
(power). All operations take the form of
enter Y, press [INPUT], enter X, [XEQ] (appropriate key).
Labels:
XEQ A: Y + X
XEQ B: Y – X
XEQ C: Y * X
XEQ D: Y/X
XEQ E: Y^X
XEQ F: “clears” the stack.
The result
shown in the display while the X value is left in the hidden display, which can
be accessed by pressing [ LS ] (SWAP).
The key codes
for the HP 20S and HP 21S are the same.
|
STEP
|
CODE
|
KEY
|
|
01
|
61, 41, A
|
LBL A
|
|
02
|
21, 0
|
STO 0
|
|
03
|
51, 31
|
SWAP
|
|
04
|
21, 75, 0
|
STO+ 0
|
|
05
|
22, 0
|
RCL 0
|
|
06
|
61, 26
|
RTN
|
|
07
|
61, 41, B
|
LBL B
|
|
08
|
21, 0
|
STO 0
|
|
09
|
51, 31
|
SWAP
|
|
10
|
21, 65, 0
|
STO- 0
|
|
11
|
22, 0
|
RCL 0
|
|
12
|
32
|
+/-
|
|
13
|
21, 0
|
STO 0
|
|
14
|
61, 26
|
RTN
|
|
15
|
61, 41, C
|
LBL C
|
|
16
|
21, 0
|
STO 0
|
|
17
|
51, 31
|
SWAP
|
|
18
|
21, 55, 0
|
STO* 0
|
|
19
|
22, 0
|
RCL 0
|
|
20
|
61, 26
|
RTN
|
|
21
|
61, 41, D
|
LBL D
|
|
22
|
21, 0
|
STO 0
|
|
23
|
51, 31
|
SWAP
|
|
24
|
21, 45, 0
|
STO÷ 0
|
|
25
|
22, 0
|
RCL 0
|
|
26
|
15
|
1/X
|
|
27
|
21, 0
|
STO 0
|
|
28
|
61, 26
|
RTN
|
|
29
|
61, 41, E
|
LBL E
|
|
30
|
21, 0
|
STO 0
|
|
31
|
51, 31
|
SWAP
|
|
32
|
14
|
y^x
|
|
33
|
22, 0
|
RCL 0
|
|
34
|
74
|
=
|
|
35
|
21, 0
|
STO 0
|
|
36
|
21, 26
|
RTN
|
|
37
|
61, 41, F
|
LBL F
|
|
38
|
71
|
Clear
|
|
39
|
71
|
Clear
|
|
40
|
61, 26
|
RTN
|
Example:
In the following
examples, 8 will be stored in the hidden register.
7 + 8: 7, INPUT, 8, XEQ A. Result: 15
7 – 8: 7, INPUT, 8, XEQ B. Result: -1
7 * 8: 7, INPUT, 8, XEQ C. Result: 56
7/8: 7, INPUT, 8, XEQ D. Result: 0.375
7^8: 7, INPUT, 8, XEQ E. Result: 5,764,801
Eddie
This blog is
property of Edward Shore, 2017