HP 33s - Manual (Page 208)

13–24 Programming Techniques
Program Lines:
(In RPN mode)
Description:

   This routine collects all known values in three
equations.

  "!1 1L2 2 Prompts for and stores a number into the variable
addressed by i.

   L Adds 1 to i and repeats the loop until i reaches
13.012.

 ! 

 !  When i exceeds the final counter value, execution
branches back to A.
Label J is a loop that completes the inversion of the 3 × 3 matrix.
Program Lines:
(In RPN mode)
Description:

   This routine completes inverse by dividing by
determinant.

 ! ª1 1L2 2 Divides element.

   L Decrements index value so it points closer to A

 !  Loops for next value.

 ! Returns to the calling program or to  ! .
Equations with (i)
You can use (i) in an equation to specify a variable indirectly. Notice that 1L2 2
means the variable specified by the number in variable i (an indirect reference),
but that i or 1L2 means variable i.
The following program uses an equation to find the sum of the squares of variables
A
through Z.