HP 35s

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HP 35s
TypeScientific calculator
ManufacturerKinpo Electronics
PredecessorHP 33s
Entry modeRPN, Algebraic
Display typeDot-matrix LCD
Display size2x14 characters (5x7px per character)
ProcessorSunplus/Generalplus 8502 (based on 6502)
Programming language(s)Keystroke
User memory32 KB RAM, ~30 KB available to user
Power supply2x CR2032

The HP 35s is a scientific calculator sold by Hewlett Packard and manufactured by Kinpo Electronics. It is the final traditional scientific RPN calculator released by HP. The HP 35s was released in 2007, as a celebration of 35 years since the introduction of the HP 35, the first handheld calculator with transcendental functions.

Overview[edit | edit source]

The HP 35s returns to a traditional RPN calculator design, away from the stylized chevron design of its predecessor, the HP 33s. The 35s is powered by a Generalplus 8502, an extension of the 6502 architecture, core alongside keyboard, power, and display circuitry in silicon. It also contains 32 KB of RAM, of which about 30 KB is accessible to the user.

The HP 35s is almost completely feature-compatible with the 33s. It adds simplified complex number operations with an 'i' key and the ability to jump to any line within a program label, making the large memory much more usable than the same memory was on the 33s.

Hardware and Software Issues[edit | edit source]

The HP 35s exhibits many well-known problems in both its hardware design and its software. For many users, various keys become unreliable over time or out of the box. The 35s also runs through its two CR2032 batteries much faster than older Saturn-based calculators.

The software of the 35s is riddled with bugs. A particularly famous bug is that the program checksum feature is not reliable, and a program's checksum can change as the contents of memory change, even if the program itself remains the same. The same issue occurs with the size of a program as displayed by the calculator. Another bug, carried over from the 33s, is the "cosine bug", which returns inaccurate results for 'sin(x)' (not cos, despite the name) near 0. A full bug list is available here.

External resources[edit | edit source]

See also[edit | edit source]