I like reading the original paper in it's original format, but here is searchable text version: https://ftp.arl.army.mil/~mike/comphist/48eniac-coding/index...

A 1948 report on the conversion of ENIAC from being programmed by a complex wiring of cables and setting switches to the more modern stored program. The writing is accessible, but the introduction and section on test programs are probably most interesting.