We got some of the first ones at the Naval Research Laboratory in Washington, DC, and I used them to perform (unclassified) molecular dynamics simulations. Peop

We got some of the first ones at the Naval Research Laboratory in Washington, DC, and I used them to perform (unclassified) molecular dynamics simulations. People used them to scale up all kinds of simulations. The language was a special dialect of C called C*, which was essentially C with array extensions that made doing arithmetic on the CM (which, as other commenters point out, was really just a big array processor) relatively easy to program. It was a single-instruction-multiple-data model, where each little processor got its own piece of the array. Then as now, the way to get speed was to minimize communication among processors.