HP HP-67 - Page 223

Controlling the I-Register 219
To run the program, key in the number of years for which you want
to see the amount. Press § to store the number of years in the
I-register and otherwise initialize the program. Then press [ to run
the program.
For example, to run the program to find the amount of the account
after 5 years; after 15 years:
Slide the W/PRGM-RUN switch wrram [l run to RUN.
Press Display
503 Program initialized.
o
After five years, in 1629,
the account would have
been worth $30.63.
1508 Program initialized.
a
49.89 After 15 years, in 1639,
the account would have
been worth $49.89.
How it works: When you key in the number of years and initialize
the program by pressing £§, the number of years is stored in the
I-register by the instruction. The year (1624) is stored in primary
storage register R,, and the amount ($24.00) is stored in primary
storage register R,.
When you then press ], calculation begins. Each time through the
loop, 5% of the amount is computed and added to the amount in
R,, and one (1) year is added to the year in R;. The instruction
subtracts one from the I-register; if the value in I is not then zero,
execution is transferred back to [ and the loop is executed again.
The loop continues to be executed until the value in the I-register
becomes zero. Then execution skips to the 1 instruction in
program memory step 021. Execution continues sequentially down-
ward from step 021, recalling the current year from R, and formatting
and displaying it, then recalling the current amount from R, and for-
matting and displaying that following the year.