| | {{infobox |
| | | title = IBM 650 |
| | | full name = IBM 650 Magnetic Drum Data-Processing Machine |
| | | announced = 1953 · first installed 8 December 1954 (John Hancock Mutual, Boston) |
| - | | technology = vacuum tubes · 4,000-word magnetic drum @ 12,500 rpm · bi-quinary decimal |
| + | | technology = vacuum tubes · 1,000–4,000-word magnetic drum @ 12,500 rpm · bi-quinary decimal |
| | | production = ~2,000 systems — the world's first mass-produced computer |
| | | fame = the machine a generation learned programming on — Knuth dedicated TAOCP to one |
| | }} |
| | |
| | # IBM 650 |
| | |
| | The **IBM 650** was the Model T of computing — the first computer *mass-produced*, nearly 2,000 systems built between 1954 and 1962, and the first to make a meaningful profit. At a fraction of the 701's price it brought computing within reach of small businesses and universities; the first unit went to John Hancock Mutual Life Insurance in Boston in December 1954, and by decade's end the 650 was *the* most popular computer on Earth.[[cite: [IBM 650](https://en.wikipedia.org/wiki/IBM_650) and [Columbia's ACIS history](https://www.columbia.edu/acis/history/) — the ~2,000 units, the John Hancock first install, and the mass-production firsts]] |
| | |
| - | The hardware was a study in squeezing a computer onto a drum: a two-address, **bi-quinary coded decimal** machine — *addresses and data both decimal* — running digit-serial at 125 kHz, with its 4,000-word drum spinning at 12,500 rpm. Every operation's cost depended on drum geography, so the 650's culture made "optimum programming" an industry: the famous **SOAP** assembler (Symbolic *Optimal* Assembly Program) existed largely to place instructions where the rotating memory would find them fastest. And because it was cheap enough to teach on, the 650 became the machine a generation learned programming on — a rotating drum full of a decade's first programs.[[cite: [IBM 650](https://en.wikipedia.org/wiki/IBM_650) — the bi-quinary decimal design, drum specs, and SOAP's optimal-placement mandate]] |
| + | The hardware was a study in squeezing a computer onto a drum: a two-address, **bi-quinary coded decimal** machine — *addresses and data both decimal* — running digit-serial at 125 kHz, with its drum — 1,000, 2,000, or 4,000 words depending on model — spinning at 12,500 rpm. Every operation's cost depended on drum geography, so the 650's culture made "optimum programming" an industry: the famous **SOAP** assembler (Symbolic *Optimal* Assembly Program) existed largely to place instructions where the rotating memory would find them fastest. And because it was cheap enough to teach on, the 650 became the machine a generation learned programming on — a rotating drum full of a decade's first programs.[[cite: [IBM 650](https://en.wikipedia.org/wiki/IBM_650) — the bi-quinary decimal design, drum specs, and SOAP's optimal-placement mandate]] |
| | |
| | # The computer Knuth remembered in stone |
| | |
| | The 650's place in culture is literally inscribed: *The Art of Computer Programming*'s dedication reads "**This series of books is affectionately dedicated to the Type 650 computer once installed at Case Institute of Technology, in remembrance of many pleasant evenings**" — Knuth learned programming on a 650 and immortalized the machine in the field's bible. Others cut teeth the same way: the 650 at a university was often the *first computer anyone on campus had ever touched*.[[cite: Knuth, *The Art of Computer Programming* dedication — the Case Institute 650 memorialized; see also [IBM 650](https://en.wikipedia.org/wiki/IBM_650)]] |
| | |
| | ```fact |
| | A 650 "program" was partly an act of geography — the instruction's next address was *part of the instruction* (two-address format), so a skilled programmer placed each next instruction exactly where the drum head would be when the current one finished. On a 12,500-rpm drum, a misplaced instruction cost milliseconds you could hear. |
| | ``` |
| | |
| | # Where it sits |
| | |
| | The 650 is the proof that *cheap* was a feature: it wasn't fast (adds took up to 10 ms), but it was *there* — in insurance offices, engineering shops, and campuses — where nothing else was. It created the mass market IBM would dominate for fifty years, and the first generation of programmers who learned that a computer was something you could actually get your hands on. |
| | |
| | ## Check your understanding |
| | |
| | - [ ] What made the 650 the "Model T" of computing — two production firsts? |
| | - [ ] What was bi-quinary coding — and what did the drum's rotation have to do with programming? |
| | - [ ] What was SOAP, and why "Optimal"? |
| | - [ ] How is the 650 memorialized in computer science's most famous book series? |
| | |
| | ```hide Show answers |
| | 1 — **first mass-produced computer** (~2,000 units) and the first to make a **meaningful profit**. |
| | 2 — **bi-quinary decimal** encoding for data *and* addresses; instruction timing depended on where data sat on the rotating drum — placement was the optimization. |
| | 3 — **Symbolic Optimal Assembly Program** — its job included placing instructions optimally on the drum. |
| | 4 — Knuth **dedicated *The Art of Computer Programming*** to the 650 at Case Institute of Technology, "in remembrance of many pleasant evenings." |
| | ``` |
| | |
| | [[Category:Hardware]] |
| | [[Category:Computing]] |
| | [[Category:History]] |
| | |
