Why not? "A code" is a software package which solves some kind of problem computationally. Plural, codes. I'm sure it's been in use almost as long as the programmable computers. Here's[1] a link to an article from 1968 which uses the term in the singular ("The MENE Neutron Transport Code".)

[1] https://www.osti.gov/biblio/4819611-mene-neutron-transport-c...