HP 49g+ User Manual
Page 670
Page 21-25
stack level 7 to give a title to the input string, and leave stack level 6 empty to
facilitate reading the display, we have only stack levels 1 through 5 to define
input variables.
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
volume(m
3
), 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
V
T
K
J
V
T
T
V
p
⋅
=
⋅
⋅
=
)
_
662902
.
1
(
2
.
0
31451
.
8
)
,
(
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: “ {“ :V: :T: “ {2 0} V }
INPUT OBJ→ → V T ‘(1.662902_J/K)*(T/V)’ »