Working with the 1st Edition UNIX code has been a blast. I just thought I'd quickly summarise the features of the 1st Edition. It's quite amazing the system that had been written by the end of 1971: - a multitasking system with up to 16 processes - multiple users - a hierachical filesystem, with empty directories used as mountpoints - read/write file protection for user/other (no group), plus the execute and set-userid bits - i-nodes, and filenames separated from i-nodes, allowing hard links - device files Just as interesting is the fact that, out of the 33 system calls in 1st Edition UNIX, only one has disappeared completely from modern UNIXes; four have merged into signal(), and a few have morphed into other syscalls: V1_RELE 0 /* release the CPU, i.e. pre-empt this process */ V1_EXIT 1 exit() V1_FORK 2 fork() V1_READ 3 read() V1_WRITE 4 write() V1_OPEN 5 open() V1_CLOSE 6 close() V1_WAIT 7 wait() V1_CREAT 8 open(path, O_CREAT | O_TRUNC | O_WRONLY, mode); V1_LINK 9 link() V1_UNLINK 10 unlink() V1_EXEC 11 exec() V1_CHDIR 12 chdir() V1_TIME 13 gettimeofday() V1_MKDIR 14 mkdir() V1_CHMOD 15 chmod() V1_CHOWN 16 chown() V1_BREAK 17 brk() V1_STAT 18 stat() V1_SEEK 19 lseek() V1_TELL 20 lseek(fd, 0, SEEK_CUR); V1_MOUNT 21 mount() V1_UMOUNT 22 umount() V1_SETUID 23 setuid() V1_GETUID 24 getuid() V1_STIME 25 settimeofday() V1_QUIT 26 signal(SIGQUIT,...) V1_INTR 27 signal(SIGINT,...) V1_FSTAT 28 fstat() V1_CEMT 29 signal(SIGEMT,...) V1_SMDATE 30 utimes() V1_STTY 31 fcntl(), tcsetattr() V1_GTTY 32 fcntl(), tcgetattr() V1_ILGINS 33 signal(SIGILL,...) The fact that we are still using these system calls today speaks volumes for the original design. Cheers, Warren