# HP 48gII User Manual Page 110

Graphing calculator.

Note: By pressing @@@p1@@ ` we are trying to activate (run) the p1 program.
However, this program expects a numerical input. Try the following exercise:
\$@@@p1@ „Ü5`. The result is:
The program has the following structure: << → r 'π*r^2' >>
The « " symbols indicate a program in User RPL language (the original
programming language of the HP 28/48 calculators, and available in the HP
49G series). The characters → r indicate that an input, to be referred to as r,
is to be provided to the program. The action from the program is to take that
value of r and evaluate the algebraic 'π*r^2'. In the example shown above,
r took the value of 5, and thus the value of πr
2
= π⋅25 is returned. This
program, therefore, calculates the area of a circle given its radius r.
RPN mode
In RPN mode, you only need to press the corresponding soft menu key label to
get the contents of a numerical or algebraic variable. For the case under
consideration, we can try peeking into the variables z1, R, Q, A12, α, and A,
J@@z1@@ @@@R@@ @@@Q@@ @@A12@@ @@ª@@
created above, as follows:
At this point, the screen looks like this:
To see the contents of A, use: L @@@A@@@.
To run program p1 with r = 5, use: L5 @@@p1@@@.
Notice that to run the program in RPN mode, you only need to enter the input
(5) and press the corresponding soft menu key. (In algebraic mode, you need
to place parentheses to enter the argument).
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