HP 12C Programming
Tricks
These tricks can help you cut steps in your
programming. Remember that it is still
important to test results. Happy
programming!
Using Last X
This can be a god-send in making programs more
efficient. Unless you are using the
Platinum Edition, we only have 99 steps to work with. The LST X function returns the x argument
that is last used in a calculation.
|
Function
|
LST x Returns
|
|
One-Argument Functions:
√, LN, e^x, FRAC, INTG, n!
|
The x pre-calculation
|
|
Two-Argument Functions (Arithmetic):
+, -, *, ÷, y^x
|
The x value in the arithmetic operation
|
Number of Inputs
I follow a general rule when it comes to the number of
inputs required on an HP 12C program. If
the number of inputs is 1 or 2, I would have the user enter inputs on the stack
and run the program. If the number of
inputs is 3 or more, I have the user pre-store
the inputs into registers before pressing [R/S] to run the program. Example:
If my program calls for a, b, and c, I have the user store a in register
0, b in register 1, and c in register 2, and then have the user press [R/S].
Branching
You can branch a program to different parts of the
program. You designate a register as a
choice variable. (Rc = 0 for option 0, 1
for option 1, etc). Examples include setting
the variable for computing combinations vs permutations, set for month payments
vs yearly payments.
See this link for an example: http://edspi31415.blogspot.com/2016/08/hp-12c-combinationbinomial.html
Program format:
RCL Rc
Test value
-
X=0?
GTO (applicable line number)
…
(applicable section)
(commands and calculations)
GTO 00 (end the program)
Multiply x by 100
Keystroke: [ENTER],
1, [x<>y], [%T]
Result: The X stack has
100*x, the Y stack has x.
Dividing x by 100
Keystrokes: [ENTER], 1, [ % ]
Results: The x stack
has x/100, the Y stack has x.
Quickly entering
numbers in the form of 10^n (n is an integer)
Keystrokes: 1, [EEX],
n
This is useful when n>2.
For example, entering 10000 takes five steps normally. With this sequence, 1 [EEX] 5, you only use
3.
Another Way to Double
Keystrokes: [ENTER],
[ + ]
Results: X Stack:
2*x. 1 program step saved.
Absolute Value of x.
Keystrokes: 2, [y^x],
[ g ] [ √ ]
Result: X Stack: |x|.
It is important to square the number first since the HP 12C’s square
root function returns an error on negative numbers.
Signum Function of x.
This is the extension of the absolute value sequence shown
previously.
Keystrokes: [ENTER],
2, [y^x], [ g ] ( √ ), [ ÷ ]
Result: X Stack:
sgn(x)
Modulus (for two
positive values)
Keystrokes: a,
[ENTER], b, [ ÷ ], [ g ] (LSTx), [x<>y], [ g ] (FRAC), [ * ]
Result: X stack: a MOD b
Comparing Values
We have a value stored in a register, call it Rc, where c
obviously can stand for 0, 1, and so on.
Keystrokes: [RCL], c, [ - ], [ g ] (x=0)
If the test is true (x = Rc), the next step is
executed. Otherwise, it is skipped.
Six Digit
Approximation of π
Since the HP 12C does not have a π button, we’ll have to
enter a 10 digit approximation of π, which will take 11 steps. However, if you want an approximation (given
most of the time the HP 12C is used on Fix 2 mode), we can use the
approximation π ≈ 355/113, which is accurate to six decimal places.
π ≈ 3.14159265359
355/113 ≈ 3.14159292035
Keystrokes: 355,
[ENTER], 113, [ ÷ ]
Calculate (1 +
n/100)^x without using the TVM Registers
Keystrokes: 1,
[ENTER], n, [ % ], [ + ], x, [y^x]
I hope you find these tricks useful. If you have any, please feel free to share
them.
Eddie
This blog is property of Edward Shore, 2016.