Hewlett Packard HP-42S

Serial Number 3112S07866: 1991, 12th week, Singapore
Accessories Pouch

Manual: RPN Scientific calculator Benutzerhandbuch (German, 1st edition July 1988, 351 pages)
Condition Very near mint. There are some small color defects below the display. ROM version C7.
Acquired Owned this since 1990
Serial Number 2942S33877: 1989, 42nd week, Singapore
Accessories None
Manual: RPN Scientific calculator Benutzerhandbuch (German, dated 3/1991, 351 pages) Excellent condition, acquired separately on 13.1.2003.
Essentially mint. Some specks of dust behind the display cover.  ROM version A7.
HP codename, series Davinci, Pioneer
Type, Precision, Input Mode Scientific, 12 BCD digits, exponent 499, Reverse Polish Notation
Programmable Yes, keystrokes
Performance Index 13. This is about 5 times as fast as the HP-41C. 
Memory Permanent memory. 8192 bytes for program and all data, program and variables shared
Display 132x16 LCD dot matrix, 22x2 characters
Special features Two line display showing X and Y register or X register and top function key assignments. Solver (root finding), matrix operations, numerical integration, complex numbers, strings, various curve fitting models. Software compatible to HP-41. Graphics capabilities and infrared port for printing.
Works with the HP Infrared Printer.
Original Pricing, Production 31.10.1988 ($120) - 1.3.1996 (approx. $120)
Batteries 3x small button sized cells
Dimensions Length 14.7cm, Width 7.8cm, Height 1.5cm
Links HP-42S RPN Scientific Calculator Owner's Manual, June 1988 (PDF)
HP-42S RPN Scientific Programming Examples and Techniques, July 1988 (PDF)
HP-42S Fast Mode.
Hardware and Software details (MoHPC)
For Machine language programming see comment about HP-17B.
Hidden matrix functions (local page).
Forensic Result8.99999864267
Comment One of HP's absolute high-end machines. It was designed to be code-compatible with the HP-41. The number of features is overwhelming and covers much of what can be found in the HP-15C and HP-32SII plus full high-resolution graphics capabilities. In the 300+ pages manual the engineers proudly note "... an efficient operating system has been developed..." - indeed this is no exaggeration! Different from the HP-32S/HP-32SII program and variable names are not restricted to a single letter but can have lenghty names like in the HP-41. 
Compared to the HP-32SII it doesn't support fractions - and it is only about half as fast. 
Its biggest disadvantage is of course that programs cannot be stored on magnetic cards or read in using a bar code wand or some serial PC interface. The serial interface came only later with the much larger HP-48.
According to Nelson M. Sicuro the ROM version of the HP-42S can be determined as follows:
  • Press ON & LOG together to enter the debugger.
  • Press the decimal point.
  • Now a character on the left and a digit on the right will be displayed briefly: This is the ROM version number.
  • Press ON & the square root button together to quit the debugger.
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