PSI - Issue 84

Galileo Tamasi et al. / Procedia Structural Integrity 84 (2026) 709–716

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invariant unimodal distribution identifies programmable calculators as a vital transitional technology between manual methods - such as slide rules and pre-tabulated handbooks - and the Personal Computer. Following a period of rapid innovation, this technology settled into a specialized niche that remains essential for infrastructural management. For modern engineers, recovering these "frozen" historical algorithms is the only reliable way to decipher original design intent and ensure the safety of aging bridge stocks.

Fig. 1. Temporal distribution of technical literature on programmable calculators (1965–2025). Adapted from Gross (2025).

3. Digital tools for retrocalculation: emulators and simulators To bridge the gap between historical design logic and modern structural validation, it is necessary to employ digital tools that can faithfully replicate the computational environment of the 1970s. While original hardware remains a valuable reference, the use of software emulators and simulators allows for systematic and numerically reliable execution of historical routines on contemporary operating systems (Windows, macOS, iOS). These tools differ significantly in their architecture: emulators recreate the specific hardware behavior by executing the original ROM code, while simulators replicate the user interface and functional logic through modern programming languages. A comparative analysis of the currently available software for the HP 67 and HP 97 (see Table 1 and Table 2) reveals a diverse landscape in terms of platform compatibility and functional completeness. For the HP 67, tools such as Nonpareil, Panamatic, and the version developed by Olivier De Smet stand out for their "Excellent" suitability for retrocalculation, as they fully support card readers and extensive card libraries.

Table 1. Comparative analysis of HP 67 emulators and simulators.

Emulator Hp 67

Card Reader

Card Library Manual

Software

Suitability for Retrocalculation

Nonpareil Panamatic

Yes Yes Yes Yes Yes

Yes Yes Yes

Yes Yes Yes Yes Yes

Free Free Free Free Paid

Excellent Excellent Excellent

Olivier De Smet

Limpid Fox

No

Perfect

RPN-67 Pro / SD

Yes

Moderate