• Unix first developed in 1969 at Bell Labs (Thompson & Ritchie).
• Originally written in PDP-7 asm, but then (1973) rewritten in the ‘new’ high-level language C.
⇒ easy to port, alter, read, etc.
•6th edition (“V6”) was widely available (1976).
– source avail
⇒ people could write new tools.
– nice features of other OSes rolled in promptly.
• By 1978, V7 available (for both the 16-bit PDP-11 and the new 32-bit VAX-11).
• Since then, two main families:
– AT&T: “System V”, currently SVR4.
– Berkeley: “BSD”, currently 4.3BSD/4.4BSD.
• Standardisation efforts (e.g. POSIX, X/OPEN) to homogenise.
• Best known “UNIX” today is probably linux, but also get FreeBSD, NetBSD, and
(commercially) Solaris, OSF/1, IRIX, and Tru64.
Ritchie and Thompson writing in CACM, July 74, identified the following (new)
features of UNIX:
1. A hierarchical file system incorporating demountable volumes.
2. Compatible file, device and inter-process I/O.
3. The ability to initiate asynchronous processes.
4. System command language selectable on a per-user basis.
5. Over 100 subsystems including a dozen languages.
6. A high degree of portability.
Features which were not included:
• real time
• multiprocessor support
Fixing the above is pretty hard.