HP 33s - Manual (Page 169)

Simple Programming 12–11
Entering and Displaying Data
The calculator's variables are used to store data input, intermediate results, and
final results. (Variables, as explained in chapter 3, are identified by a letter from A
through Z or i, but the variable names have nothing to do with program labels.)
In a program, you can get data in these ways:
„ From an INPUT instruction, which prompts for the value of a variable. (This is
the most handy technique.)
„ From the stack. (You can use STO to store the value in a variable for later
use.)
„ From variables that already have values stored.
„ From automatic equation prompting (if enabled by flag 11 set).
(This is also handy if you're using equations.)
In a program, you can display information in these ways:
„ With a VIEW instruction, which shows the name and value of a variable.
(This is the most handy technique.)
„ On the stack — only the value in the X–register is visible. (You can use PSE
for a 1–second look at the X–register.)
„ In a displayed equation (if enabled by flag 10 set). (The "equation" is usually
a message, not a true equation.)
Some of these input and output techniques are described in the following topics.
Using INPUT for Entering Data
The INPUT instruction ( { ‰ Variable ) stops a running program and
displays a prompt for the given variable. This display includes the existing value
for the variable, such as
@
)

where
"R" is the variable's name,
"?" is the prompt for information, and
0.0000 is the current value stored in the variable.