Re: byteoffset() in lutf8lib.c from 5.3, work2

[Tim Hill <drtimhill@...>]

On May 14, 2014, at 12:19 AM, Coroutines <coroutines@gmail.com> wrote:

> On Wed, May 14, 2014 at 12:09 AM, Tim Hill <drtimhill@gmail.com> wrote:
> 
>> Well now, there is a *very* good reason for DEL being at 127 .. and only old-timers like me (and maybe Dirk) would know it :)
> 
> I'm thinking it's related to punch cards -- punching out 7 holes
> across the line would "delete" the character.  7 bits punched in a
> signed 8-bit number is 127?
> 

Pretty much .. though it’s paper tape not punched cards .. a “hole” was a 1, non-hole a 0, so the only way to erase a character was to punch out ALL the holes, hence 127 (the 8th bit was nominally a parity bit). In fact, DEL is really “IGNORE” since when reading the tape and 127 codes were usually silently skipped by the computer or reader.

—Tim