Software Engineering Fundamentals

Each line of code is an opportunity for a bug to occur: Keep programs as short as possible.

Bugs will only be fixed if the code paths they lie in are executed: Have tests and testers.

No one language is best at everything: Use appropriate tools for each job.

To maintain simplicity you need to build on top of previous work: Divide code into logical modules/libraries that can ge reused.

Each line of code is an opportunity for a bug to occur: Keep programs as short as possible.

This is inconsistent, the right would be
"Each line of code is an opportunity for a bug to occur: Keep the lines in your code at the minimum."
But in most languages you could have whole programs in only one line.
Or
"Each character in your code is an opportunity for a bug to occur: Keep programs as short as possible."
But this includes new spaces, comments and lines.

No one language is best at everything: Use appropriate tools for each job.

I would appreciate a example. I can't see why anyone would use anything other than C and their favorite lisp dialect for any reason (except lazyness).