HP 35s Scientific Calculator - Manual (Page 158)

10-8 Vector Arithmetic
Creating Vectors from Variables or Registers
It is possible to create vectors containing the contents of memory variables, stack
registers, or values from the indirect registers, in run or program modes.
In ALG mode, begin entering the vector by pressing 
3
. RPN mode works
similarly to ALG mode, except that the d key must be pressed first, followed by
pressing 
3
.
To enter an element containing the value stored in a lettered variable, press h
and the variable letter.
To enter an element from a stack register, press the < key and use the Õ or Ö
keys to move the underline symbol so that it is under the stack register to be used
and press

To enter an element indirectly indicated by the value in the I or J register, press
h and either (I) or (J).
For example, to construct the vector [ C, REGZ, (J) ] in RPN mode, press d
3
, then hC <Õ h
A
.