What are programs?

Curiously enough, the books and references about software development and software engineering I have read...

«There are people who prefer to anchor themselves in the comfort of a limited level of knowledge. They consider themselves practical and 'real-world'-ish»

— Andrei Alexandrescu

«This is the answer to our question. Programs aren't physical objects,such as reams of source code or fluctuating current -- they're INTENTIONS... the intention that a particular type of programmable system exhibit specific behavior. A program is the carefully formulated will of its creator, solidified into a form which a programmable system can use. The program of a player piano is a SONG, not a roll of paper. The program is the intention that the piano play a certain melody. The song is expressed as punches in paper, but the paper is not the program, any more than a portrait is a person.»

— Source: https://lists.tunes.org/archives/tunes/1999-January/001874.html