Ok, I was trying to understand exactly what the alloc(III) subroutine does in unix version 5 and I've discovered that the source code for it appears to be missing. In Unix v6 there is a file in the TUHS archives V6/usr/source/s4/alloc.s so I assume there should be a V5/usr/source/s4/alloc.s as well but I can't find it anywhere. In v5 the command "ar t /lib/libc.a" lists the files in the c library and that includes alloc.o so there should be a source file somewhere. Mark