# HP 50g User Manual Page 672

Graphing calculator.

Input string program for two input values
The input string program for two input values, say a and b, looks as follows:
"Enter a and b: " {" :a: :b: " {2 0} V } INPUT OBJ
"
«
This program can be easily created by modifying the contents of INPTa. Store
this program into variable INPT2.
Application: evaluating a function of two variables
Consider the ideal gas law, pV = nRT, where p = gas pressure (Pa), V = gas
3
volume(m
), n = number of moles (gmol), R = universal gas constant =
8.31451_J/(gmol*K), and T = absolute temperature (K).
We can define the pressure p as a function of two variables, V and T, as p(V,T)
= nRT/V for a given mass of gas since n will also remain constant. Assume
that n = 0.2 gmol, then the function to program is
T
J
T
p
(
V
,
T
)
. 8
31451
0
2 .
. 1 (
662902
_
)
V
K
V
We can define the function by typing the following program
V T '(1.662902_J/K)*(T/V)'
"
«
and storing it into variable @@@p@@@.
The next step is to add the input string that will prompt the user for the values of
V and T. To create this input stream, modify the program in @@@p@@@ to read:
"Enter V and T: " {"
:T: " {2 0} V }
«
:V:
V T '(1.662902_J/K)*(T/V)'
"
INPUT OBJ
Store the new program back into variable @@@p@@@. Press @@@p@@@ to run the program.
Enter values of V = 0.01_m^3 and T = 300_K in the input string, then press
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