The character set used is MacRoman, as ASCII is only defined between 0 and 127. Displaying 30 characters at a time also misses the point, as ASCII is nicely defined into four chunks of 32. And character sets are 0-based, even if 0 is only NUL.

It should show what the characters mean if they don't print, even, perhaps, for space.

And then, if it supports MacRoman, it should support other character sets (iso-latin-1 and windows-whatever, perhaps).

It's also horribly slow, nothing I couldn't have in a text file, and I use 'man ascii' anyway.