HP 35s User Manual page 3

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HP 35s Indirect register data packing program
storage registers starting with 100 and working down. This can cause quite a shock when you're not expecting it in a
program or calculation.
Each indirect register, like each direct register and each stack register, can hold a variety of objects, such as a real
number, a complex number, or a 2-D or 3-D vector. Since these take varying amounts of memory to hold them, the HP
35s allocates 37 bytes per register for each location, whether the register needs that many bytes or not (see page 14-24
of the HP 35s user's guide). This means that a group of indirect registers that are only going to hold a real number are
only using 1/3 of the possible storage space per register.
To reclaim some of this space that might otherwise be unused, it is possible to pack three real numbers into a 3-D vector
and store the group into a single indirect register. This can save a tremendous amount of calculator memory. Storing 100
real numbers using indirect registers normally would use 3700 bytes. Packing them using the program in this learning
module will only use 1/3 of that memory, which will then be available for other uses.
This program originally appeared in Datafile, a publication of HPCC. HPCC is a voluntary, independent body run by and
for users of handheld and portable computers and calculators. The club has been helping members for more than 20
years to get the most from their Hewlett Packard equipment and to further the exchange of information and ideas. You
can find out more about HPCC at their website
The program listing. Program length is 338 bytes. Checksum C4F6. RDN is < (Roll Down). All flag-related instructions
(SF, CF, and FS?) are accessed through ¹·. The conditional tests (x=0?, x<0?) are accessed through
º. In several areas of this program, stack manipulations occur that look rather odd but manage to preserve the
pre-existing stack contents. RPN mode is assumed in the program and throughout these instructions. The program uses
one global label, variable register I, and flags 0, 1, 2, and 3.
Y001 LBL Y
Y002 CF 0
Y003 CF 1
Y004 CF 2
Y005 CF 3
Y006 x=0?
Y007 GTO Y062
Y008 x < 0?
Y009 SF 0
Y010 ABS
Y011 RDN
Y012 IDIV(REGT-1,3)
Y013 STO I
Y014 RDN
Y015 LASTx
Y016 ABS
Y017 RDN
Y018 RMDR(REGT-1,3)
Y019 x=0?
Y020 SF 1
Y021 FS? 1
Y022 GTO Y030
Y023 RDN
Y024 REGT-1
Y025 x=0?
Y026 SF 2
Y027 FS? 2
Y028 GTO Y030
Y029 SF 3
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Y030 RDN
Y031 FS? 1
Y032 [ 1, 0, 0 ]
Y033 FS? 2
Y034 [ 0, 1, 0 ]
Y035 FS? 3
Y036 [ 0, 0, 1 ]
Y037 RCLx (I)
Y038 FS? 0
Y039 GTO Y058
Y040 +/-
Y041 RDN
Y042 XEQ Y063
Y043 RCL+ (I)
Y044 RDN
Y045 ABS
Y046 CLx
Y047 LASTx
Y048 RDN
Y049 XEQ Y063
Y050 RDN
Y051 REGZ+REGT
Y052 STO(I)
Y053 RDN
Y054 LASTx
Y055 LASTx
Y056 CLX
Y057 +
Y058 CF 0
- 3 -
Y059 CF 1
Y060 CF 2
Y061 CF 3
Y062 RTN
Y063 FS? 1
Y064 REGTx[ 1, 0, 0 ]
Y065 FS? 2
Y066 REGTx[ 0, 1, 0 ]
Y067 FS? 3
Y068 REGTx[ 0, 0, 1 ]
Y069 RTN
Y070 STO I
Y071 [ 0, 0, 0 ]
Y072 STO(I)
Y073 DSE I
Y074 GTO Y072
Y075 STO(I)
Y076 CLSTK
Y077 RTN
HP 35s Indirect register data packing program - Version 1.0