The HP42s is a high-end RPN calculator in the HP Pioneer line. Launched in 1988, It was originally meant as a HP 41C replacement and thus had FOCAL compatibility, capable of running most HP 41C programs with little modification. However it was hampered in this role due to its lack of extensions and limited I/O capabilities, and was discontinued early (as compared to HP 17B) in favour of HP 48SX in 1995.
| Type | Scientific calculator |
|---|---|
| Introduced | 1988 |
| Discontinued | 1995 |
| Predecessor | HP 41C |
| Successor | HP 32S, HP 48SX |
| Calculator | |
| Display type | Dot-Matrix LCD |
| Programming | |
| Other | |
Overview
There are three major revisions of HP 42s: A, B and C respectively. Revision A and B have a plastic pane in front of the LCD whereas revision C has a recessed LCD display. Revision C is the most commonly seen variant today.
HP 42s used a silicon-on-sapphire Saturn architecture chip code-named "Lewis" with 64K of integral ROM and a RAM controller capable of addressing up to 64KB of memory, driving a 131x16 dot matrix display. 8KB of SRAM is soldered on board and roughly 7000 Bytes are available to the user as program steps or registers.
Internally, the HP 42s is extremely similar to both the HP 17B & BII, and HP 27S, with the exception of the lack of an extended ROM chip which on the 17 series contained international language & error message and on the HP 27S contained additional instructions. On the HP 42s, this position remains unsoldered. However, the instruction to jump to this memory location is still retained.
One notable feature that it shares with HP 17B and HP 27S is its capability to print to a thermal printer using infrared. The corresponding thermal printer is the HP 82240. It is the only calculator in the Pioneer line capable of utilizing the graphics printing capability of the 82240, while other calculators in the line are limited to printing characters.
The HP-42s runs on SysRPL with many low level assembly language tweaks, and thus it supports many advanced features like the HP 28C series. For example, it treats complex values as an object taking up one stack level (instead of consuming two stacks on the HP 41C or having a separate imaginary stack as on the HP 15C). It also supports plotting to LCD with each pixel being individually addressable, and thus capable of drawing or plotting under program command. However unlike the HP 28C, it supports only 4 stack levels and does not have built-in plotting utilities, requiring the user to program their own.
Like other Pioneers, HP 42s ships with a debugger and self-test routine.
There are only two known bugs on the HP 42s.
Hardware Mods
Some users have reported success replacing the RAM chip of their HP 42s with up to 32KB of RAM and modifying the LC circuit to force the chip to run at twice the clock speed. However it must be noted due to the construction of Pioneers calculators, opening a HP 42s involves drilling heat-stakes and thus will irreversibly reduce its structural integrity.
Tricks
*note: the top row of keys are customarily labeled A-F from left to right.
HP 42s has two resets: Master reset which puts the calculator back to "factory condition", clearing all memory with On+A+F and Machine reset with On+C which interrupts any program, clears certain flags and set the calculator into a state ready to receive user input again. As with the HP 27S and HP 17B, the self test is triggered with On+D. On the first screen of the self test routine hitting backspace (<-) will put the calculator in debugger. In this state the Up/Down keys, divide/multiply keys, plus/minus keys can be used to increment or decrement the current memory address by 1000,100 and 1 nybble(s) respectively.