The Voyager Series
The HP-15C was part of Hewlett-Packard's Voyager series — a family of horizontally-oriented calculators that redefined portable computing in the early 1980s. Widely considered the finest scientific calculator ever made, the 15C packed matrices, complex numbers, integration and root solving into the same shirt-pocket form factor as the rest of the line.
1981: The Voyager Series Launches
Hewlett-Packard introduced the Voyager series with the HP-11C Scientific and the HP-12C Financial calculators. They brought HP's new horizontal form factor and the Nut processor architecture, along with continuous memory that preserved programs and data even when the calculator was switched off. The HP-12C went on to become one of the best-selling calculators of all time and is still manufactured today.
- New horizontal "Voyager" form factor
- Based on the Nut CPU (1LF5 series)
- Continuous memory — programs survive power-off
- HP-12C still in production over 40 years later
1981: The HP-11C
The programmable scientific workhorse. The HP-11C packed a full set of scientific functions, statistics, and keystroke programmability into a slim shirt-pocket package — the everyday RPN scientific that preceded the advanced HP-15C in the Voyager lineup.
- Trigonometric, hyperbolic, logarithmic and exponential functions
- Statistics with linear regression
- 203 bytes of keystroke-programmable memory
- RPN entry with a 4-level stack and continuous memory
1982: The HP-15C
The Advanced Scientific. Widely considered the finest scientific calculator ever made, the HP-15C built on the 11C's foundation with matrix operations, complex number arithmetic, numerical integration, and a built-in root solver — all in the same shirt-pocket form factor. It became a cult classic among engineers and remains one of the most sought-after RPN calculators ever produced.
- Matrix operations up to 8×8 — MATRIX, DIM, (i), I, RESULT
- Complex number arithmetic — Re⇆Im, full complex trig and transcendentals
- Numerical integration (∫xy) and the SOLVE root finder
- 448 bytes of keystroke-programmable memory with labels, branches, tests, flags and loops
- Direct and indirect storage in up to 67 registers
- Display control in FIX, SCI and ENG — angle modes DEG, RAD, GRD
- RPN entry with a 4-level stack and continuous memory
1982: The HP-16C
The Computer Scientist's calculator — the only calculator ever designed specifically for programmers and hardware engineers. It worked natively in hexadecimal, octal and binary, with bit manipulation, boolean logic, and variable word size.
- Number base modes: HEX, DEC, OCT, BIN
- Bit operations, shifts, rotates and masks
- Boolean logic and 1's / 2's complement arithmetic
- Unique among all calculators ever made
1982: The HP-10C
The entry-level Voyager. A basic programmable scientific calculator that completed the series lineup, offering core RPN functionality at an accessible price point.
- 79 program lines
- Basic scientific functions
- The rarest Voyager today
1989: End of Production
The HP-15C was discontinued in the late 1980s, but its reputation endured. Praised for its build quality, intuitive RPN feel, and dependable battery life, well-kept units remain sought after by collectors and RPN enthusiasts who still reach for a Voyager over anything modern.
Legacy & Influence
The Engineer's Specialist
Where the 11C was the everyday all-rounder, the HP-15C was the specialist — the Voyager that engineers reached for when the job needed matrices, complex arithmetic, or a numerical solver. Its blend of advanced capability and pocketable size made it one of the most respected scientific calculators HP ever shipped.
RPN & the HP Way
Like all HP calculators of its era, the 15C used Reverse Polish Notation (RPN) — a postfix notation that eliminates the need for parentheses and matches the way stack-based machines actually work. Once it clicks, RPN feels less like a feature and more like a way of thinking.
Key Features of the HP-15C
The HP-15C packed an extraordinary range of advanced math and programming functionality into a shirt-pocket device. Here are the capabilities that made it a classic.