Paul Ford in 2014:

As far as I can tell, no truly huge world-shifting software product has ever existed in only one version (even Flappy Bird had updates). Just about every global software product of longevity grows, changes, adapts, and reacts to other software over time.

So I set myself the task of picking five great works of software. The criteria were simple: How long had it been around? Did people directly interact with it every day? Did people use it to do something meaningful?

I came up with:

• the office suite Microsoft Office,
• the image editor Photoshop,
• the videogame Pac-Man,
• the operating system Unix,
• and the text editor Emacs.

Ford’s criteria felt more interesting than those of the other similar lists:

I propose a different kind of software canon: Not about specific moments in time, or about a specific product, but rather about works of technology that transcend the upgrade cycle, adapting to changing rhythms and new ideas, often over decades.

This – about Unix – also caught my attention:

There’s a sad tendency in most manuals and programming guides to congratulate people simply for thinking. Not here; you’re expected to think. That can be very exciting when you’re used to being patronized, and it’s one of the best things about Unix.