For those who are using the book Modern Quantum Chemistry. An Introduction to Electronic Structure Theory by Szabo and Ostlund, there is an example SCF code in Appendix B. It is written in Fortran IV which is troublesome to maintain and also to build in the first place.
For a bit of fun I rewrote the code in C and have made it freely available to anyone who wants it. See my Github link below.
https://github.com/pm133/SCF_Szabo