I hit an odd, though not critical bug in the display of assembly language code on the question Disassembler for intel 8080. There's a block of assembly code where the format is:

opcode operand1 operand2   comment

for each line. The poster originally formatted it using a block quote, but noted that it didn't look right. I changed it to be formatted as code, but saw something odd.

When I first did it, I hadn't lined up the comments. So I went back and lined them all up. While editing, the live preview showed that the first 3 lines had one less space before the comment than was actually there. This was odd, but I thought I'd just add a space to those lines. In the live preview they now lined up. But when I pressed the button to save the edits, suddenly they had 1 extra space in the actual display of the assembly code and they no longer aligned.

So I edited it again and removed the extra space. Sure enough the code in the editor looked fine, but the preview showed 1 too few spaces on those lines. But when I saved it, they came back and everything aligned.

They are caused by tabs, and yes, tabs are "evil" on Stack Exchange. They break code formatting.

Here is shown on the real post, no problem!

real post: correctly aligned

This is shown in the editor, still looks good!

editor: correctly aligned

And this is shown in the preview... hmm?

preview: comments on line 3-5 are missing a whitespace

Finally, this is shown on the revision's source... eh?

revision source: too many tabs on line 1&7

The fix is easy but cumbersome: don't use tabs, align (manually) with spaces instead.

  • Ah, OK. That makes some sense. I couldn't figure out what was wrong and basically just modified what was already there. Seems odd that in pre-formatted text with monospaced fonts that tabs would be an issue, but I guess that's where we are. Thanks for the explanation. – user1118321 Aug 4 at 17:42
  • 2
    "align (manually) with spaces instead" please don't do that by hand but use an editor converting tabs to spaces instead :-) – Mast Aug 5 at 6:57

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