Subject: Re: MIT ChaosNet code port to Linux
From: Erik Naggum <>
Date: Fri, 21 Jun 2002 02:35:46 GMT
Newsgroups: comp.lang.lisp
Message-ID: <>

* (James A. Crippen)
| Really?  7 bit?  That doesn't fit very well into a 36 bit word...  I
| know it was supported in most systems for ASCII obviously, but didn't
| think that it would be used internally in whatever OS was running...

  Yes, 7-bit files were the norm on TOPS-10 and -20.  That wastes one bit for
  every 5 characters.  A byte would never cross a word boundary.  When writing
  binary files for 8-bit computers, two models were used: one that used normal
  8-bit bytes and wasted a nybble at the far end of each word, and one that
  used 9-bit "quarter-words" where the extra bit was used for parity.  I used
  one of these tools to build binaries for various 8-bit controllers and even
  compiled Kermit for a CP/M-based system.

| What do you put in the other of the word once you've
| stuffed in the five 7-bit characters?  Maybe a parity bit?

  Zero.  The editor SOS could actually store a five-digit line number with this
  spare bit set to one, and several text processing tools, such as compilers,
  would know to ignore this word.  It is still quite amazing that people worry
  about what a spare bit could be used for, while their gigabyte machines spend
  99.8% of their CPU power pondering how to idle more efficiently.
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