First useful program supplied to other was an IBM 7040 assembly language implementation of the random number function RANDU. It was written in 196X (X > 4). I gave it away to engineering students. It greatly sped up an assignment which was some sort of simulation. They had been using the FORTRAN equivalent library function which was written in FORTRAN and not optimized (FORTRAN compilers of that era didn't do optimization. JFW