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--- systems:2nd_edition [2023/05/20 17:07] – fix links segaloco
+++ systems:2nd_edition [2026/04/30 10:09] (current) – segaloco
@@ Line 6: / Line 6: @@
 **Documentation: ** [[https://www.tuhs.org/Archive/Distributions/Research/Dennis_v2/v2man.pdf|2nd Edition man pages]]
-The second edition of Unix was developed for the PDP-11 at Bell Labs by Ken Thompson, Dennis Ritchie and others. It extended the First Edition with more system calls and more commands. This edition also saw the beginning of the C language, which was used to write some of the commands.
+The Second Edition of Unix was developed for the PDP-11/20 at Bell Labs by Ken Thompson, Dennis Ritchie and others. It extended the First Edition with more system calls and more commands. This edition also saw the beginning of the C language, which was used to write some of the commands.
+The Second Edition, like the first, was only designed to run on the unprotected PDP-11/20 and requires the Extended Arithmetic Element to simulate some operations which would later be supported natively on the PDP-11/45 and other models. This would be the last PDP-11/20 unprotected version of UNIX, as the following Third Edition represents an intermediary PDP-11/45 assembly version of the system and the kernel is rewritten in C before the Fourth Edition.
 The code in the Unix Archive is only the source to some of the commands, some of the library functions, and the C compiler. The files in c/ come from the [[https://www.tuhs.org/Archive/Applications/Early_C_Compilers/last1120c.tar.gz|last1120c.tar.gz]] tape, and form a working C compiler for Second Edition Unix.
@@ Line 40: / Line 42: @@
   * The tmg compiler-compiler is introduced
   * The fc Fortran compiler replaces the old for compiler
-  * The linker now supports the Explor language
+  * The linker now supports the [[https://www.tuhs.org/pipermail/tuhs/2023-May/028430.html|Explor]] language
   * Libraries move from /etc to /usr/lib
@@ Line 63: / Line 65: @@
   * The UNIX Time-sharing System - D.M. Ritchie, K. Thompson
-For more information about Second Edition Unix, see [[https://www.bell-labs.com/usr/dmr/www/hist.html|The Evolution of the Unix Time-sharing System]] by Dennis Ritchie.
+For more information about Second Edition Unix, see [[https://www.nokia.com/bell-labs/about/dennis-m-ritchie/hist.html|The Evolution of the Unix Time-sharing System]] by Dennis Ritchie.