undergraduate student: reading lecture notes and textbooks
graduate student: reading papers and monographs
employed engineer: reading specifications and laws
retired engineer: ?
graduate student: reading papers and monographs
employed engineer: reading specifications and laws
retired engineer: ?
@amiloradovsky I did read x86 assembly, Ada, geochemistry and English dictionaries 
(I don't remember and I'm not representative in this regard, I only remember reading OpenBSD man pages~)