When the University of Louisville upgraded their main IBM 360/30 Computer from 16K of memory to 64K. Remember a K is just 1024 bytes.

We use to have to run one of the PAYROLL Programs in 2 passes. One to do the calculations and the second to print the checks, because there was not enough memory, to perform both functions at once.

And then there was 1967 when Reynolds Metals Co did the entire USA billing on a IBM 360/20 with a punch card compiler. No disks at all.