Scrollback Gripe

Why is the default scrollback setting always so small? This applies to DOS, XTerms, terminal emulators like putty (which could really do with a way to save the scrollback setting too).

How much memory does a 10,000 line scrollback cost? Let’s knock ourselves out and assume it’s full unicode – four bytes per character. On 80 wide, that’s 320 bytes per line. So the entire scrollback is 3.2MB. Being even more hedonistic, let’s have ten such terminals, for a total of 32MB. Modern computers come with 1GB or more, so the cost is negligible, and any installer should make use of the computer’s capabilities. Benefit of not losing vital information: priceless.

0 thoughts on Scrollback Gripe

  1. Programmers which hack such applications love optimization and work with damn old computers :-D…

    That’s a typical Open Source phenomen, sensles optimizing with a big lack of usability…

    (don’t get me wrong, I love open source)…

  2. Hi !

    I deseagree totaly on what you say. 3.2 MB is a lot, and sometimes, you are happy to use an OLD computer with 32 or 64 MB of RAM. That would be up to 10% of the total amount of memory.

    I have used a lot putty with windows 98 and 16 MB of RAM. I’m happy it worked without having to twick it, but it’s true the scrollback could have be set up to 1000 or 2000 lines (which wouldn’t eat too mutch memory and would be still enough).

    If you have a lot of memory, then increase the default value. When it comes to coding, you always have to consider worst case.


  3. Hi Thomas,

    I agree that 3.2MB is a lot on an old PC, and that programmers should always consider the worst case (more specificially, the worst case that is actually a valid case).

    But should considering the worst case mean that we downplay all the other cases, even if they are far more common? That’s a “lowest common denominator” approach to design. Applied to TV, we’d have no colour shows until the last die-hards give up their black-and-white units.

    In this case, I think the solution is in the installer. It can choose sensible defaults based on the machine’s profile. That’s something surprisingly few applications do. I can think of some parallels though. Operating systems usually suggest default cache or swap size based on disk space. And I think games are quite good about determining useful defaults. Other programs could benefit from those features. Why do browsers use a fixed cache size, for instance? If the program’s going to choose a default anyway, it may as well make a good guess.

  4. “putty (which could really do with a way to save the scrollback setting too).” In the Configuration window where you choose which “Session” to use [You get it at startup], select Window from the list of Categories on the left. About halfway down the window as now displayed is a box to control lines of scrollback. Fiddle with that. then pick Sessions from the Categories list again and save your session. Then it will be there for you next time. HTH.

  5. Hugh,

    Thanks for your post! I’ve been wanting a more secure way to copy router NAT table entries longer than 300 lines for a while now – and your advice was just the ticket. Good-bye, Hyperterminal!

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