THE was the first multiprogramming operating system beating IBM to the punch.
The THE system apparently introduced the first forms of software-based memory segmentation (the Electrologica X8 did not support hardware-based memory management)[1], freeing programmers from being forced to use actual physical locations on the drum memory. It did this by using a modified ALGOL compiler (the only programming language supported by Dijkstra's system -- Dijkstra implemented the first compiler for ALGOL) to "automatically generate calls to system routines, which made sure the requested information was in memory, swapping if necessary."
Apart from this, Dijkstra is the inventor of all shortest path algorithm (used in the link-state routing in the Internet), opened the self-stabilizing systems field, which was again very influential in several internet and sensor networks protocols.
Dijkstra refused to classify himself as a theorist or systems person.
BTW, Knuth would probably be the first person to object to your comment.
It was a real question. Only an idiot would question Dijsktra's well-known contributions to CS. My issue is that his profuse judgmental statements about practical system-building strike me as misguided. When I read those of his writings he sounds like an intolerant theorist in a bubble.
From the web pages I've read, it's not clear that THE was ever used. It's also not clear what Dijsktra actually did on Algol. Indeed I always thought it was Naur, not Dijsktra, who is associated with making the first good Algol compiler. Also, Dijsktra is described as having "led the team" on these projects, which is ambiguous.
I'm happy to be wrong, but it would certainly be interesting if Dijsktra's disastrous (to my mind) pronouncements about how to make software were grounded in deep experience with successfully making it. It would be much less surprising if they were grounded in brilliant theoretical work and a habit of telling other people they're doing everything wrong.
Edit: it's my fault for being cryptic, but inventing algorithms does not count as what I meant by "making" something, i.e. building a working software system that people use. Anybody who's heard of Dijkstra knows that he invented algorithms.
Edit: but then I like Beethoven better than Mozart too :)
