Subject: Re: RFC: /kern/summary
To: John F. Woods <>
From: Steven J. Dovich <>
List: tech-kern
Date: 03/11/1999 10:04:48
> > 	I thought that, historically, Unix has used six character identifiers
> > 	(later seven chars) and no underscores for lack of space.
> >My understanding was that the first six were required to be UNIQUE.  That
> >is you could have as many characters as you cared to use, but the compiler
> >was only required to use the first 6.  
> Does anyone have an original-edition C Programming Language handy?
> As I recall, the V6/V7 PDP-11 linker truncated external symbols at 7
> characters, preserving case; but the linker used on one of the other
> machines V6 ran on insisted on 6 characters monocase.  I'm almost certain
> this is discussed in the first or second chapter of the original CPL, but
> my carefully-archived(*) copy is at home.

The Reference Manual portion of the original CPL set the limit at
no more than 8 chars, though more could be used. It then goes on
to note that external identifiers may have tighter constraints
due to assemblers and loaders. The most restrictive environment
noted there was the Honeywell 6000 with a 6 char monocase limit
for external identifiers.