HP -16C Owner's Handbook Manual page 93

Section 9: Program Branching and Controls 91
The following program sums all the bits in the bit pattern in a
given storage register, yielding a checksum. The contents of
storage registers R, through R, are sequentially checksummed. As
the bits are summed, they are added to the updated, double-sized
checksum being held in registers Y and Z. This is what the stack
contains just before line 012:
T
2 Current checksum: most significant word.
Y Current checksum: least significant word.
X Number whose bits will be summed and added to
the current double-word contents in Y and Z.
The resulting checksum will be placed in registers X and Y.
This program uses to decrement a register pointer in the
Index register and to control conditional loop branching.
Keystrokes Display
(a][P/R] 000-
CLEAR 000-
[g)[L8] D 001-43,22, d
(f]SETCOMPL[UNSGN] 002- 42 3 Unsigned mode for
adding bits.
4 003- 4
004- 4244 Word size four bits.
005- 23
A 006- A
007- 44 32 Stores number of top
register (R,) in R;.
0 008- 0
009- 36 Initializes checksum
to 0.
(g](LBL]O 010-43,22, 0 Start of summing loop.
(Enables stack lift.)
(RCL]((i)] 011- 4531 Recalls contents of
current register whose
numberis stored in R;.