Subj : Re: Computers
To   : Spectre
From : tenser
Date : Mon Jul 22 2024 13:55:37

On 22 Jul 2024 at 10:48a, Spectre pondered and said...
 
 Sp>  MP> It was the first form that I was aware of for sure.  IIRC, there was 
 Sp>  MP> kind of service, or site, where I had to use uudecode on files that w
 Sp>  MP> not received via email, too.  I may very well be remembering that wro
 Sp>  MP> I am not sure why they'd need encoding if they were not transmitted v
 Sp>  MP> email or usenet.
 Sp> 
 Sp> There were a lot of early systems out there that were 7bit... if you
 Sp> tried to push data through these you'd lose some. UUENCODEing made it
 Sp> all 7bit for safe transfer. It was lossy though, a UUd file was larger
 Sp> than the original.

Depends on what you're transferring.  uuencode takes 8-bit
data and packs it into a 6-bit alphabet, in 60-column records,
preceded by a character count (encoded as a printing character)
and succeeded by a newline (so up to 62 characters, total).
That leaves up to 60 characters containing data, for a total
of 60*6=360 bits of data max per line, or 360/8=45 bytes; put
another way, 3 bytes packed into 4 characters, so 45 bytes per
60 character line.

So you've got a 25% efficiency loss for the encoding, plus the
count and line-break overhead, that's around over 3%.  Call it
30% overhead relative to the source data.

But if you compress the original, and _then_ uuencode it, you
might come out ahead: if you're compression ratio is around 2:1,
then you're still smaller than the original by 20% or so.

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