HP HP-67 - Page 238

234 Using the I-Register for Indirect Control
5
3
o
014 35 74| Otherwise, display the
contents of all the pri-
mary storage registers.
o 015 31 42
o
0 Restores contents of
secondary storage
registers for possible later
calculations.
0 078 34 34
0 019 35 22
When the program is run, it begins by clearing the storage registers
and placing 25 in the I-register. Then execution begins, recalling the
current value in the I-register and storing that number in the
corresponding address—for example, when the I-register contains the
number 17, that number is recalled and stored in the storage register
(Rs7) that is addressed by the number 17. Each time through the loop,
the number in the I-register is decremented, and the result is used
both as data and as an address by the instruction. When the
number in the I-register reaches zero, execution transfers out of the
loop and the contents of all primary storage registers are displayed by
the automatic register review function.
To run the program:
Slide the W/PRGM-RUN switch werem [lll[lIruN to RUN.
Press Display
o
24.00
etc.
Notice that the contents of the I-register have been decremented to
zero.
You do not have to address secondary storage registers Rg, through
Rsy indirectly by using (@ and [@. In some cases,
in fact, using the function in conjunction with (@ and
(@ can be a powerful programming tool, since you can use the
same instructions to process two sets of data.