Off the top of the screen

In a recent conversation with a (somewhat younger) colleague, I uttered the phrase "scrolled off the top of the screen". I wanted to convey the notion of information that was not available at the present, but was available in the past.

As I used the metaphor, I realized that my (somewhat younger) colleague had most likely never used an honest-to-goodness real text-only terminal. With today's large-memory computers and graphic environments, the ability to scroll up and see previous content (for some types of windows) is taken as granted. But in the old days, when computers were large boxes locked away in secure rooms, users interacted with terminals, and terminals had limited memory and limited display capabilities. So limited that they displayed text in only one font and had no scrolling. (What you saw was all that there was.)

On these terminals, new text (usually) appeared at the bottom. When the screen was full of text and new text appeared, the top line was removed, all remaining lines were moved up one line, and the text appeared in the new, now blank, line at the bottom. This action was called "scrolling", named so because it mimicked the action of terminals that used paper in long rolls.

It strikes me that the verb "scroll" was kept when windowing environments displayed text that could be moved up and down.

But I digress. Let us return to the notion of information that is not available at present, but was available in the past.

Consider the programming skills needed to build data structures. I spent a good deal of time in college developing, testing, and debugging programs that built data structures and sorting algorithms. Today, such structures are baked into languages. Perl, Python, Ruby, C#, Java, and even C++ with its STL extensions all have data structures and sorting, available to the developer essentially "for free".

Asking an aspiring programmer to build such structures seems a waste of time, similar to asking an author to build their own typewriter or a taxi driver to refine their own gasoline. We have better things to do than to re-invent elementary constructs that are available (and debugged).

These skills of data structures have scrolled off the top of our collective screen. At least for the general developers.

General developers do not need to learn these skills. (Nor do they need to learn assembly language, or the ASCII code, or proper writing for programming sheets.)

But someone has to remember them. Languages like Python have these constructs, but they are available because someone put them in the general library. The Python language rests on the Python library, which in turn rests on libraries common to multiple languages, which in turn rest on functions provided by the operating system which in turn rest on functions private to the operating system. But there is an end, a definite stopping point. It is not "elephants all the way down".

Some language engineer must be available to add basic constructs to the language, and that means that some engineer must know the concepts. Skills may scroll off the top of the screen for the typical developer, but as an industry, we must retain them.

We're going to need an attic.