@jeff As a very early coder, you are so right about those constraints. In 1968 or so I was supporting suites of structural analysis program that had to operate in a max memory of 12,000 24-bit words (48 Kbytes) with no disk. We did 250-node grid and planeframes, or 100-node 3D structures. Matrix inversion (by Newton's decomposition) between 2 tape drives was a sight to see! I had to include an operator-console countdown to convince the Operators (!) not to cancel the jobs for apparent looping.