If they come in a library or as part of the language, that's an even better reason why you should understand how they work. If you live in a world where a line

If they come in a library or as part of the language, that's an even better reason why you should understand how they work. If you live in a world where a line of code assigns a variable or dereferences a pointer or emits adds and imuls, you can probably get what's happening just looking at the code. If each line of code manipulates complex structures, sends queries to the database, interfaces with the network etc, you'd better know what you're doing and you'd better know it well.