HP 35s User Manual

							 
 
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HP 35s  Programming using line numbers 
 
 
 
 
Programming the HP 35s 
 
Using line numbers rather than labels 
 
Example 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   
						

							 
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HP 35s  Programming using line numbers 
 
hp calculators - 2 - HP 35s  Programming using line numbers - Version 1.0 
Programming the HP 35s 
 
Doing a simple calculation once on the HP 35s is easy. Doing the same calculation many times, or doing a complicated 
calculation, takes longer. It can be better to store all the steps needed for the calculation in a program. A program is a 
set of instructions, stored all together. Once it is written, it can be tested to see if it works correctly. Then it can be used 
many times, without the need to press every key of the calculation each time. 
 
A simple program is just a set of keystrokes stored so that they can be carried out with one key. The HP 35s provides 
many commands to let programs do more, for example stop and ask for input, or show an intermediate result. This 
training aid concentrates on simple programming; it also shows a few of the more advanced programming commands. 
 
Using line numbers rather than labels 
 
The HP 35s has 26 labels for use to define programs or transfers to locations within programs. Unlike the HP 33s, the 
HP 35s also includes the ability to transfer execution to specific line numbers within one of the 26 labels. This allows for 
a much greater utilization of program memory without using labels excessively. 
 
For example, the program line below illustrates how a goto instruction can now branch to a line number within a lettered 
label. Step B010 tests whether the value in the X register is less than the value in the Y register. If true, step B011 
transfers execution to step 018 of label B. On the HP 33s, step B011 would have required a goto instruction pointing to a 
step with one of the 26 labels. 
 
 Figure 1 
 
In the past, using line number GTO and XEQ instructions in programs was difficult if changes were made to the program 
after these instructions were entered, since the program steps would have changed but the transfer instructions would 
still have pointed at the old line numbers, making the program work incorrectly. 
 
The HP 35s removes this constraint. When a program containing line number GTO or XEQ instructions has a step added 
or deleted, the HP 35s dynamically changes the lines referred to by these instructions to point at the correct location. 
For example, if in the program shown in figure 1 above, another step were added before step B010 such as an ABS 
instruction, steps B010 would become step B011 and step B011 would become step B012. More importantly, the HP 35s 
would change the new step B012’s GTO instruction to continue pointing at the same location within the program – step 
B019 in this instance. This is shown in figure 2 below. 
 
 Figure 2 
 
This dynamic renumbering allows for the use of line numbers in GTO or XEQ instructions without the drawbacks earlier, 
less-advanced calculators may have had.   
						

							 
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HP 35s  Programming using line numbers 
 
hp calculators - 3 - HP 35s  Programming using line numbers - Version 1.0 
In detail, the HP 35s handles changes in a program containing line number GTO and/or XEQ instructions as follows: 
 
Edit performed HP 35s program dynamically changed so that 
A step is inserted before a GTO or XEQ instruction All GTO and XEQ instructions are renumbered to point to 
 the revised (higher step number) location 
 
A step is deleted before a GTO or XEQ instruction  All GTO and XEQ instructions are renumbered to point to 
 the revised (lower step number) location 
 
The step pointed to by a GTO or XEQ instruction is deleted Any GTO or XEQ instructions continue to point to the  
 same instruction. The instruction that now fills the  
 previous step number is the destination of the transfer  
 instruction. 
 
The HP 35s now offers the ability to take advantage of a large program memory capacity, limited only by a user’s 
imagination. 
 
Example 1: Rewrite the program from page 14-4 of the HP 35s User’s Guide to use only one label. Use line numbers 
for all transfer instructions. 
 
Solution: The program as presented on page 14-4 looks like this: 
 
S001   LBL S 
S002   INPUT A 
S003   INPUT B 
S004   INPUT C 
S005   INPUT D 
S006   RCL D 
S007   RCL C 
S008   RCL B 
S009   RCL A 
S010   X2 
S011   XEQ Q001 
S012   XEQ Q001 
S013   XEQ Q001 
S014   SQRT 
S015   RTN 
Q001   LBL Q 
Q002   X  Y 
Q003   X2 
Q004   + 
Q005   RTN 
 
 Steps S011 through S013 would need to be changed to point at the step after S015 RTN. Since we will be 
removing the LBL Q instruction, steps previously labeled Q002 through Q005 will now be right after step 
S015 RTN. They would now be labeled S016 through S019. The XEQ instructions found at steps S011 
through S013 should now point to step S016. The revised program using only one label is shown below. 
 
S001   LBL S 
S002   INPUT A 
S003   INPUT B 
S004   INPUT C 
S005   INPUT D 
S006   RCL D 
S007   RCL C 
S008   RCL B 
S009   RCL A 
S010   X2 
S011   XEQ S016 
S012   XEQ S016 
S013   XEQ S016 
S014   SQRT 
S015   RTN 
S016   X  Y 
S017   X2 
S018   + 
S019   RTN 
 
 The program is not only one total line shorter but uses only one label. Consistent use of line number GTO 
and XEQ instructions allows for better utilization of the 26 letter labels. 
   
						

							 
 
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HP 35s  Accessing the stack registers 
 
 
 
 
The stack registers 
 
Examples 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   
						

							 
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HP 35s  Accessing the stack registers 
 
hp calculators - 2 - HP 35s  Accessing the stack registers - Version 1.0 
The stack registers 
 
The HP 35s uses an operational stack of four registers, called X, Y, Z and T and LASTx. In RPN mode, these registers 
are used to hold values for computations. In algebraic mode, these registers hold results from previous calculations. 
 
Chapter 2 of the HP 35s User’s Guide explains the RPN stack in detail. Many of these features work in algebraic mode 
as well. 
 
In RPN mode, these stack registers are easily accessed using the !, #, !$ and % keys whether in 
a program or in normal computations. Access to these registers within algebraic mode is essentially the same, but the 
way the HP 35s presents these registers to the user is slightly different. 
 
Examples 
 
The examples shown below indicate some of the ways the stack registers can be accessed within algebraic mode as 
well as using this type of access in RPN mode within programs. Many efficiencies can be achieved in RPN mode using 
these approaches. 
 
Example 1: Compute 1 + 2 then 3 + 4 and then divide 5 by the sum of the previous two results in algebraic mode. 
 
Solution: &() 
 
 Figure 1 
 
*+) 
 
 Figure 2 
 
,-!4# 
 
 Figure 3 
 
At this point, the HP 35s displays the four level stack with the cursor beneath the Y register. This register 
contains the first calculation we did above (the 1 + 2). Pressing ) will copy a reference to this register 
back to the calculation in progress as shown below. REGY stands for “register Y.” 
 
 Figure 4   
						

							 
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HP 35s  Accessing the stack registers 
 
hp calculators - 3 - HP 35s  Accessing the stack registers - Version 1.0 
#.) 
 
 Figure 5 
 
#.)  (REGX stands for “register X.”) 
 
 Figure 6 
  
)  (This completes the calculation) 
 
 Figure 7 
  
Answer:  The answer is 0.5. The larger point is the ability to reference up to four previous results when in algebraic 
mode. 
 
Example 2: In RPN mode within a program, fill the stack with 1, 2, 3, and 4. Then divide the 4 by (1+2x3), but do so 
without losing any of the stack register contents. 
 
Solution: !/&))())*))+ 
 
 Figure 8 
  
(Note: the )key is pressed twice above in order to terminate digit entry upon the first press and then 
to actually place an ) into the program when pressed the second time). At this point, the four level 
stack is full of the four values. If you were to attempt to enter the 7 for the division, the 1 that was entered 
first would disappear off the top of the stack. However, the following technique can be used to operate 
upon a number located in the X register without losing any values from the stack. 
 
The technique involves rolling the value in X down to the T register and then entering an equation that 
operates upon the T register to perform the calculation. This can be quite an involved expression. The 
result will be placed into the X register and the previous contents of Y, Z, and T are preserved. 
 
#0 
   
						

							 
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HP 35s  Accessing the stack registers 
 
hp calculators - 4 - HP 35s  Accessing the stack registers - Version 1.0 
 Figure 9 
  
# 
 
 Figure 10 
  
11) 
 
 Figure 11 
  
-4&(2* 
 
 Figure 12 
  
) 
 
 Figure 13 
  
Answer:  The lines entered into this program would, when executed, take the value that was originally in X and divide 
it by ( 1 + 2 x 3 ) without disturbing the stack. While this is actually a mixing of algebraic features within the 
RPN mode, it provides HP 35s users with a tremendous ability to control the calculator. 
 
 
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HP 35s  Indirect register data packing program 
 
 
 
 
The HP 35s and indirect registers 
 
Saving program memory space 
 
Saving indirect storage space 
 
The program listing 
 
Usage instructions 
 
Entering program lines 
 
Line by line analysis of the program 
 
Saving keystrokes 
 
Usage examples 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   
						

							 
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HP 35s  Indirect register data packing program 
 
hp calculators - 2 - HP 35s  Indirect register data packing program - Version 1.0 
 
 
The HP 35s and indirect registers 
 
The HP35s contains registers or variables that can be referenced directly or indirectly. Variables A through Z can be 
directly addressed, as in a !# instruction. Indirect addressing uses two of these direct variables as indices that 
hold the location or address where an operation is to be performed. The two variables that are used this way are $ and 
%. The indirect registers begin at address 0 and can go up to 800, if the user allocates that many. That is 801 additional 
storage registers compared to the earlier HP 33s calculator. 
 
It is also possible to address the direct variables and the statistics variables indirectly using addresses of -1 through -32. 
Address -1 would refer to the direct variable #, address -26 would refer to the direct variable &, and -27 trough -32 
would refer to the statistical summation registers. This is shown in a table on page 14-22 of the HP 35s user’s guide. 
 
The way indirect addressing works is to store the number corresponding to the register you wish to use in either $ or 
%. Then you perform a !7 or !A (or any other allowed operation). For example, if you wish to 
recall a value stored in direct register #, you can either press # or store -1 into $ by !7 and then 
perform a 7. Both will recall the value stored in A.  
 
At first glance, that may not appear to be worth doing, since it takes more key presses to use the indirect method. 
However, where it becomes very useful is when you need to work with a lot of numbers, often within a program, or when 
you may not be able to know in advance where the number you wish to use is stored. 
 
Saving program memory space 
 
For example, suppose you have 20 numbers you wish to sum. A direct program might be written having these numbers 
stored in # through (. The program to sum them (which would take 41 lines of code and at least 120 bytes of 
memory), might look like: 
 
A001   LBL A 
A002   RCL A 
A003   RCL B 
A004   + 
A005   RCL C 
A006   + 
A007   RCL D 
A008   + 
… 
A039   RCL T 
A040   + 
A041   RTN 
 
On the other hand, a program using the indirect registers might have the numbers stored in indirect locations 1 through 
20. The program to sum the 20 values might look like this one. This program only takes 10 lines of code and only 32 
bytes of code. Sure, developing the second program might take a little more time than the first, but it comes at a great 
reduction of program memory space used. 
 
A001   LBL A 
A002   20 
A003   STO I 
A004   RCL (I) 
A005   DSE I 
A006   RCL (I) 
A007   + 
A008   DSE I 
A009   GTO A006 
A010   RTN
 
Saving indirect storage space 
 
To allocate a portion of the HP 35s memory to hold indirect registers, store a non-zero value into the highest register 
needed. If you need 100 registers to hold numbers and if locations 0 to 99 will work for your need, storing a non-zero 
value into indirect storage location 100 will allocate HP 35s calculator memory to create the block of indirect registers 0 
through 100. Warning: If you store a zero into memory location 100, the HP 35s will dynamically reclaim all zero indirect