For all the people dismissing lines of code as a metric, I want to point out that very early on a line of code was literally a CPU instruction. While there was certainly something to be said for efficiency of your subroutine, lines of code was not a totally unreasonable measurement of things that your program was doing. Obviously we get removed from that the more we abstract and well constructed code is different from lines of code, but I can see where they were coming from.
One of those CPU instructions (or one class of them anyway) is called a jump. It allows you to move to a different instruction than the next one, including going backwards. There has always been reusability of already written code in digital computers. LOC was no more or less meaningful when code was written in assembly or machine language than it is today.
It only measures something loosely correlated with progress toward completion and only if you know what done looks like.
