What's "code-as-procedure" supposed to be? Denotation? And how could "code-as-procedure" fail to be easy to express using "code-as-data"? Isn't it more essent

What's "code-as-procedure" supposed to be? Denotation? And how could "code-as-procedure" fail to be easy to express using "code-as-data"? Isn't it more essential that "code-as-data" should be easy to express in "code-as-text"? (As that's where languages like Lisp and ML, that have quasiquotation, excel).