On Thu, May 01, 2008 at 01:47:33PM -0400, Brad Parker wrote: I managed to scan in the 2nd Edition manuals, and they are available as a PDF here: http://minnie.tuhs.org/Z/2ndEdManuals/unix_2nd_edition_manual.pdf [ That URL is guaranteed to be ephemeral; Al, could you copy it to bitsavers? ] The skew on some of the pages comes from the photocopy that I have. Apologies. 1st Edition a.out headers were 0405, 12 bytes long. 2nd Edition a.out headers were 0407, 14 bytes long. In terms of the userland binaries we have from this era (on the s2 tape at http://www.tuhs.org/Archive/PDP-11/Distributions/research/1972_stuff/s2-bit…) some binaries are 0405 and others are 0407. Here are the 0405 ones: bin/: bin/mv bin/ar bin/od bin/bas bin/pr bin/cat bin/rew bin/chball bin/rmdir bin/check bin/roff bin/chown bin/sh bin/cmp bin/skip bin/cp bin/sort bin/date bin/stat bin/db bin/stty bin/dc bin/su bin/df bin/sum bin/du bin/tap bin/echo bin/tm bin/ed bin/tty bin/exit bin/wc bin/form bin/who bin/goto bin/write bin/if etc/getty bin/login etc/glob bin/ls etc/init bin/mail etc/msh bin/mesg etc/suftab bin/mkdir Here are the 0407 ones: bin/as usr/fort/fc1 bin/cc usr/fort/fc2 bin/ds usr/fort/fc3 bin/fc usr/fort/fc4 bin/find usr/jack/a.out bin/ld usr/jack/x.o bin/maki usr/lib/c0 bin/nm usr/lib/c1 bin/size usr/lib/crt0.o bin/strip usr/lib/fr0.o bin/un usr/sys/a.out etc/as2 As you can see, as and as2 are 0407, hence they are V2 binaries, and so would be likely to output the V2 header. I haven't read the the OCR'd kernel source fully yet; in the section for exec(), there must be code to parse an a.out header. Does it only know about 0405, or 0407, or both? Hope this helps, Warren