In May 1963, a small team at the RAND Corporation in Santa Monica flipped the switch on a JOHNNIAC computer running something nobody had ever built before: a fully interactive, conversational programming environment where a scientist could sit at a Model 33 teletype, type a mathematical expression, and get an answer back in under a second. It was called JOSS — the JOHNNIAC Open Shop System — and it was designed by Cliff Shaw, one of the co-authors of the first AI program (Logic Theorist, 1956) alongside Allen Newell and Herbert Simon.

JOSS wasn't a compiler. It wasn't a batch language. It was something radical for 1963: a conversational language where the user and the machine took turns. You typed Set x = 3.14. and the machine acknowledged. You typed Type x*2. and it responded 6.28 instantly. Line numbers stored programs; unnumbered commands executed immediately. Sound familiar? That's because JOSS invented the interactive REPL pattern that BASIC (1964), APL (1966), Python, and every Jupyter notebook cell you've ever run inherited directly.

The technical achievement was staggering for the hardware. JOHNNIAC was a 1953-vintage vacuum-tube machine with 4,096 words of Williams-tube memory. Shaw's team squeezed a full-precision decimal arithmetic system (nine significant digits, no binary rounding surprises — chosen because scientists expected decimal answers), a natural English-like syntax, structured control flow with if/do/step constructs, and a full multi-user time-sharing scheduler out of a machine that had less RAM than a modern smartwatch's stack pointer. By 1964, up to ten simultaneous users were sharing JOHNNIAC across RAND's engineering offices.

Then JOHNNIAC was retired in February 1966. JOSS was ported to a PDP-6 (JOSS II), then to a PDP-10. It ran productively at RAND until 1978. But here's the tragedy: JOSS never left RAND. It was internal-use software, unpublished commercially, licensed to almost nobody. Meanwhile, IBM was pushing the System/360 as the future of computing — and the System/360's design philosophy was batch job submission with punched cards. IBM sales culture actively discouraged interactive computing as wasteful of machine time. When Dartmouth's Kemeny and Kurtz built BASIC in 1964, they explicitly cited JOSS as inspiration, but simplified it (they dropped the decimal arithmetic, dropped the structured control flow) to fit on cheaper hardware. BASIC won the mindshare. JOSS's superior design — decimal math, structured constructs, elegant syntax — died in the Santa Monica microfilm archive.

Why revive it now? Three reasons converge in 2026:

• Decimal arithmetic is having a renaissance. IEEE 754-2008 standardized decimal floating-point; Python's decimal module, Java's BigDecimal, and every financial system on Earth already agree that binary floats are the wrong default for human-facing numeric work. JOSS was right in 1963.
• Notebook computing has hit a complexity wall. Jupyter's hidden state problem — cells executed out of order producing mysterious results — is exactly the failure mode JOSS's ordered, line-numbered program model prevented. JOSS's design cleanly separated immediate mode from stored program mode; modern notebooks conflate them.
• The syntax was genuinely better than what replaced it. Do part 3 for i = 1(1)10. is more readable than the FORTRAN DO 100 I=1,10 that dominated science for 30 years. LLMs generating code today would benefit from a language that reads like the specification.

The JOSS manuals still exist. RAND published them as R-366 (1964) and R-5046 (1966). Someone with a weekend and a parser generator could resurrect the language exactly — and possibly rediscover why interactive computing was better before we forgot how to design it.