Supdup Alternatives

supdup reviews and mentions

• Ask HN: What was it like to use BBS in the good old times?
  2 projects | news.ycombinator.com | 7 Nov 2021

  ITS Emacs (the original TECO verision) using the SUPDUP display protocol supported "line saving", so it could tell your terminal to stash a line in memory before overwriting it, so later it could almost instantly redisplay that line when you scrolled back to it. That was really great at 300 baud. 1200 baud too, of course. But modems used to cost about a dollar a baud.

  https://github.com/PDP-10/supdup/blob/master/supdup.mss#L635

  I posted this earlier about the Gosling Emacs screen redisplay algorithm. That was the code that RMS rewrote.

  https://news.ycombinator.com/item?id=26114104

  To be fair, RMS a right to fuss and complain, because UniPress did kind of pull the rug out from under him. The display update optimization code that Gosling wrote was pretty ugly but amazingly brilliant dynamic programming stuff, and it had a skull-and-crossbones warning in the comments.

  RMS originally used the display update code from Gosling Emacs, but then rewrote it all from scratch for later versions of Gnu Emacs, after UniPress threatened him not to use it. As modems and networks became faster, and people started using window systems instead of terminals, having an "Ultra-hot screen management package" became less important. But it's a really cool algorithm, a great example of dynamic programming, and Gosling even published a paper about it!

  https://news.ycombinator.com/item?id=22849522

  James Gosling's Emacs screen redisplay algorithm also used similar "dynamic programming techniques" to compute the minimal cost path through a cost matrix of string edit operations (the costs depended i.e. on the number of characters to draw, length of the escape codes to insert/delete lines/characters, padding for slow terminals, etc).