# The HP 35s Calculator: a revised review

A while ago, I wrote a blog article on a different blog regarding the HP 35s programmable calculator. Depending on where you buy it, it could cost anywhere from \$55 to \$98 to buy.

I have heard in other places about the plastic used to make this calculator. It is indeed cheap plastic. It certainly feels hollow when you hold it. It belies the amount of memory and the increased calculating power that lies inside. The calculator has two calculation modes: ALG mode (algebraic mode) to resemble conventional calculators, and RPN mode (reverse-Polish notation), which, for those who do long calculations, provides a way to avoid parentheses, but requires getting used to stacks.

As far as RPN mode goes, only four numbers can be pushed on to the stack at maximum for this calculator. I have read other reviews for other HP calculators where the stack can be much larger. The numbers push to the bottom of the stack as you enter new numbers, and as you enter them, the “bottom” of the stack actually moves “up” on the display. It makes it difficult to discuss how it implements this data structure because the numbers scroll in the opposite direction. The theory goes that you “push” data to the top of the stack, and you “pop” data off the top of the stack. This is a LIFO data structure (LIFO = “last in, first out”). To see the HP25s implementation, you apparently “push” data to the bottom of the stack, numbers “above” it move upward, and then you “pop” data off the bottom of the stack. It actually amounts to the same thing in the end. It is still a LIFO data structure. Pushing a fifth number on to the stack will cause the first number to disappear, so you can only work with four numbers at a time.

So, let’s say that you have the following stack:

```a: 8
b: 7
c: 6
d: 5```

The last two numbers entered are the numbers “6” and “5” in memory locations “c” and “d” respectively. Operations will be done on the last two numbers entered. So, if I now press the operator “+”, it will add 6 to 5 and pop both of these numbers off of the stack.

```a: 0 (empty)
b: 8
c: 7
d: 11```

The stack rotates down, the “bottom” (location “a”) of the stack becomes empty, and the “11”, the result of the calculation replaces both 6 and 5.

Some operators are unary, so pressing the square root will perform an operation on only the last number (location “d”), and replace the result back into location “d”, eliminating the number 11.

```a: 0 (empty)
b: 8
c: 7
d: 3.31662479036```

Well, there is also the programmability of the calculator. There are many commands available, and one pet peeve is how you are only allowed to assign a single letter to name a program.

# Installing Windows 7 with the Patience of a Saint…

Here follows the installation (re-imaging) of Windows 7 on my laptop, an HP TouchSmart TM2, a refurb which I recently acquired this past Christmas. It has been giving me a litany of grief, to the point where it has been declared essentially unusable, except for updates done in a slightly different way next time to try new things. It has been repeatedly been sent back to HP, and due to a BIOS error regarding a fan (possibly the CPU fan), they replaced the mainboard instead. The BIOS errors hadn’t returned, but the BSOD’s did. Since the entire unit had been replaced earlier, then I suspect, though I have no evidence to back me up, that HP took the motherboard out of the old unit (for which I complained about repeated BSOD errors), and put it in this one, which had no other issues than the BIOS/Fan issue. I took the unit from the repair depot this past Friday, and that same night I started having a BSOD.

[Fri PM] After a BSOD incident last night, I re-imaged the hard drive,
the MB replacement may have had compatability issues with the existing
installation, which did not appear to have changed.

[Sat AM]There are a bazillion updates coming from all directions, not all
me to focus on one update at a time. The last time I tried to obey all
updates at once (about two months ago), it bluescreened. The TM2 seems
to be quite a delicate machine. Am disconnecting all devices, including the
network.

I am considering a MINT installation at this point.

[Sun 6AM]The crashes seemed to have stopped after the 134 or so updates
were appled for the second time. In the process, however, it seemed to
selecting them. These were for drivers and so on that are for devices on
my motherboard.

It reboots, then it needs another 16 “important” updates. Once again, I
am thinking that I should wait for those “optional” updates until later.
I sense the machine is “delicate”, but hard to know “in what way” is it
delicate? The installation of the 16th update is taking forever (System

I am aware that there is a ton of crapware on this machine, including a
lot of un-registered software. I need to delete as much of it as
possible.

[8AM] 4 updates failed, and things look strange. I ignore the situation,
and re-run the updates, and things go as before. Now it wants to install
another 10 updates. One of the failures was due to corruption of a file.
My guess it was from a file that was being downloaded during one of the
bluescreens. After a reboot, no further errors (for now).

[9AM] The 6 optional updates mentioned earlier regarding the drivers
for my mainboard components (video, touchscreen, etc) disappeared when I
attempted to run Windows Update again, but reappeared when I checked
again for updates. I checked the history, and it seemes their status was
“cancelled” as of yesterday (last I saw these options was today, before

3 of the updates failed, and when I checked the history to see which
ones did, I find that there have been easily over 100 failed updates,
mostly due to this earlier file corruption that was never dealt with
(at least as far as I could tell with several random checks of these).

[9:30AM] Probably time to re-image my hard drive again. But before shutt
down, another update needs to hijack my computer for installation (which
will be gone anyway after the re-imaging). Oh, and then “configuring
windows updates”… Even though all this is going to be blasted away, I
am afraid to turn off my computer.

[9:38] I find that the “minimized image recovery” is the best, since it
reformats the entire hard drive. I am glad I am in the habit of saving
documents to separate drives. So, it gets the go-ahead. This should have
been the main way to do this from the start. I don’t need to worry about
lost files, so no backup is necessary.

[3:30PM] After running errands about town and tutoring math to a
student, I begin setup so that software and drivers are being configured
on the laptop.