Why are functions useful in programming?

"Defining and using functions in programming has numerous advantages. The most obvious advantage is that it allows you a way to organize code. By separating a program it into distinct units of code it is more organized and it is clearer what each piece or segment of code does. This also facilitates top-down design: one way to approach a problem is to split it up into a series of subproblems until each subproblem is either trivial to deal with, or an existing, “off-the-shelf” solution already exists for it. Functions may serve as the logical unit for each subproblem. Another advantage is that by organizing code into functions, those functions can be reused in multiple places either in your program/project or even in other programs/projects. 133"