Wednesday, February 6, 2013

After the HP-41C

HP28C Opened
The HP-41C series remained as Hewlett Packard's top calculator for 8 years. In 1987, HP took a new direction and introduced the HP-28C, a graphing calculator with a new operating language called RPL. It featured the ability to enter and solve equations symbolically. The packaging also made a radical departure from the traditional slab style by replacing it with the so-called "clam shell" case. The left side of the case had an alphanumeric keyboard while the right side had the traditional scientific keyboard. The display was an LCD matrix which allowed to display either 4 lines of data or a graph.

The RPL programming language was not as intuitive as the former RPN. It came with two user's guides, totaling about 675 pages demonstrating the complexity of the calculator. This and the lack of ability to import or export programs limited the popularity of the model for programming development and sharing. On the other hand, its extensive built-in library of math, statistical, conversion and financial functions made it extremely powerful.
HP-28C Closed

Infrared Printer
Shown here (above and right) is a 28C that I found on eBay. Since the 28C was very quickly superseded by the HP-28S in 1988 having 4x the memory, the 28C does not fetch a very high price. This one was fully working with a good battery compartment (a common problem) and in otherwise good condition except for a blemish on the front cover.

The HP-28C had the ability to wirelessly connect to a printer via an infrared transmitter. Shown here (left) is one I found on eBay for not much. This model printer is still sold today to connect to HPs current graphing calculators.

HP enthusiasts were not happy with the move away from the intuitive RPN to RPL. To answer their concern, HP introduced in 1988 the HP-42s. This calculator was compatible with the HP-41C series but offered a more compact package and utilized a unique menu system which allowed to reduce the number of keys and the number of functions assigned to one key. While it had all the functionality of the earlier HP-41C, it lacked connectivity. It could not import or export programs and it could not connect with peripherals.

Free42 - an HP-42s Emulator for the iPad
With these two calculators, the HP-42s and the HP-28S, HP would start on a dual product line.  The former would be the traditional non-graphing RPN calculator with sequential programming. The later, a line of graphing calculators based on RPL. The HP-28S remained in production until 1992 when it was replaced by a more advanced graphing calculator without the clam-shell design, the HP-48 series. The HP-42s continued to 1995 with no real replacement. Other lower function RPN scientific calculators would follow, but the HP-42s remains among the most coveted calculators by HP enthusiasts. Prices on eBay start around $150 and go as high as $400 for boxed examples. For this reason, I don't have one of these (yet). I do however have an emulator app called Free42 that runs on my iPhone and iPad. It does everything that the original does, but for free!

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