HP HP-67

Section 11
Controlling the I-Register
The I-register is one of the most powerful programming tools avail-
able to you on your HP-67. In a preceding section, Storing and
Recalling Numbers, you learned about the use of the I-register as a
simple storage register, similar to registers R, through Rg, R, through
Rg, and Rg, through Rge. And of course, you can always use the
I-register this way, as another storage register, whether you are using
it as an instruction in a program or operating manually from the
keyboard.
Using the instructions [sT1], [fll, and in conjunction with other
instructions, you can specify the storage register addresses of and
GGEH, the label addresses of , G=3), and (GSE ), or the number of
digits displayed by the £E3 instruction. By storing a negative number
in the I-register, you can even transfer execution to any step
number of program memory. The (5Z) and instructions
permit you to increment (add 1 to) or decrement (subtract 1 from)
the current value in I, while and allow you to incre-
ment or decrement any storage register. These are features
that you will find extremely useful in controlling loops.
Storing a Number in I
To store a number in the I-register, you can use the (3 operation.
For example, to store the number 7 in the I-register:
Ensure that the W/PRGM-RUN switch wrerem IlI[IRUN is set to
RUN.
Press Display
70
(s70
213