HP 33s - Manual (Page 204)

13–20 Programming Techniques
Indirectly Addressing Variables and Labels
Indirect addressing is a technique used in advanced programming to specify a
variable or label without specifying beforehand exactly which one. This is
determined when the program runs, so it depends on the intermediate results (or
input) of the program.
Indirect addressing uses two different keys: “ (with  ) and ” (with ‘ ).
The variable I has nothing to do with ” or the variable i. These keys are active
for many functions that take A through Z as variables or labels.
„ i is a variable whose contents can refer to another variable or label. It holds a
number just like any other variable (A through Z).
„ ” is a programming function that directs, "Use the number in i to determine
which variable or label to address."
This is an indirect address. (A through Z are direct addresses.)
Both “ and ” are used together to create an indirect address. (See the
examples below.)
By itself, i is just another variable.
By itself, ” is either undefined (no number in i) or uncontrolled (using whatever
number happens to be left over in i).
The Variable "i"
Your can store, recall, and manipulate the contents of i just as you can the contents
of other variables. You can even solve for i and integrate using i . The functions
listed below can use variable "i".
STO i INPUT i DSE i
RCL i VIEW i ISG i
STO +,–, Ч ,ч i
³ FN d i x < > i
RCL +,–, Ч ,ч i SOLVE i