CP-67/CMS, at the IBM Cambridge Scientific Center at 545 Tech Square. Also in that building was the MIT Multics project and the early days of the MIT AI Lab. CP-67 ran on the /360 mod 67 and later on quite a few of the /370 mainframes. It was written mostly in System/360 Assembler, and later in IBM's double-secret language PL/S.

I taught a graduate course at Brown on the internals of TSS/360, CP-67, and Multics in the early 1970s. One year the class project was to replace the paging and tasking support of CP-67. We also did a nice little hack that gave CP-67 users virtual disks that were actually implemented as virtual memory pages. Prior to that the smallest virtual disk was a megabyte, and we only had 240 MB of real disk storage, but this allowed disks as small as 4K, which meant we could give Brown students accounts.

I've often said that Multics was a vast improvement on all of its successors, including UNIX, Linux , Mach, and maybe even NeXTSTEP.

We had a grad student who did his thesis on flowchart programming at Brown U. -- in 1966. You drew flowcharts on the IBM 2250 display and the underlying code could be FORTRAN, PL/I, or System/360 Assembler.

I did a system for the Navy in the early 80s that let you code sonar systems for the AN/UYS-2 in dataflow diagrams. It's still in use.