This is a family of computers. It was a big success. It appears that this was a big unification project of previous architectures. And it also gave software portability guarantees with future systems, since writing software was starting to become as expensive as the hardware itself.
This was the first major commercial computer hit. Stlil vacuum tube-based.
Video 1. Learning how to program on the IBM 650 Donald Knuth interview by Web of Stories (2006) Source. It was decimal!
Video 1. The IBM 1401 compiles and runs Fortran II by CuriousMarc (2018) Source.