This is the beginnings of a alternative version of the PDP-7 Unix

system which corresponds to a later development point, around mid-1971,
where the system had lost the "dd" directory and gained . and ..
entries. This is close to the system as described in
http://www.tuhs.org/Archive/PDP-11/Distributions/research/McIlroy_v0/UnixEditionZero.txt
except there are no pathnames.

To use this version: cd build; make alt; make altrun

src/cmd/init.s

@@ -124,8 +124,12 @@ login:
 2:
    lac nchar
    sys setuid		" Set the user's user-id
-   sys chdir; dd	" and change into the "dd" directory
-   sys chdir; dir
+#ifdef NO_DD
+   sys chdir; dotdot	" Change into the root directory (out of system)
+#else
+   sys chdir; dd	" Change into the "dd" directory
+#endif
+   sys chdir; dir	" and then the user's home directory
 
    lac d2		" Close file descriptor 2
    sys close
@@ -249,6 +253,8 @@ m3:
 m3s = .-m3
 dd:
    <dd>;040040;040040;040040
+dotdot:
+   <..>;040040;040040;040040
 dir:
    040040;040040;040040;040040
 

src/other/wktchrm.s

@@ -0,0 +1,41 @@
+" Alternative chrm: chrm file [file file ...]
+"
+" Unlink the named files
+
+   lac 017777			" Go to the argc
+   tad d1			" Skip past the argc
+   dac 2f			" Save pointing at cmd name, we will skip later
+   lac 017777 i			" How many arguments do we have?
+   sad d4
+     sys exit			" None, so exit
+   tad dm4			" Subtract 1
+   dac 017777 i			" and save in the argc
+
+1:
+   lac 017777 i			" Any arguments left?
+   sna
+     sys exit			" No, exit the program
+   tad dm4			" Subtract 4 from the argc and update it
+   dac 017777 i
+   lac 2f			" Move up to the next filename
+   tad d4
+   dac 2f			" and save it in the unlink arg
+   sys unlink; 2:0		" Unlink the file
+   sma
+     jmp 1b			" Loop back if the unlink was OK, or issue err
+   lac 2b			" Copy the filename pointer below
+   dac 2f
+   lac d1			" Write the filename on stdout
+   sys write; 2:0; 4
+   lac d1
+   sys write; 1f; 2		" Write " ?\n" on stdout
+   jmp 1b			" and loop back
+
+1:
+   040077;012000		" String literal " ?\n"
+dd:
+   <dd>;040040;040040;040040	" Filename dd
+d1: 1
+d4: 4
+d5: 5
+dm4: -4

src/other/wktls.s

@@ -23,7 +23,9 @@ argloop:
      jmp setlong
 
    lac argptr		" It wasn't -l, so save it as the dir to open
+#ifndef NO_DD
    dac 8f
+#endif
    dac 9f
    skp
 
@@ -79,7 +81,11 @@ entryloop:
    lac bufptr
    dac statfile		" Copy the pointer to the status call
    lac statbufptr	" Get the file's details into the statbuf
+#ifdef NO_DD
+   sys status; statfile:0
+#else
    sys status; 8:curdir; statfile:0
+#endif
    spa
      jms fileend
 

src/sys/s2.s

@@ -4,7 +4,13 @@
 	" file status (stat) system call
 	" AC/ pointer to status (inode) buffer + i-num (13 words)
 	"   sys status; dir_name_ptr; file_name_ptr
+	"   NO_DD version: sys status; file_name_ptr
 .status:
+#ifdef NO_DD
+   jms arg			" fetch file name pointer
+   dac .+3
+   lac u.cdir			" get current working directory
+#else
    jms arg			" fetch directory name pointer
    dac .+5
    jms arg			" fetch file name pointer
@@ -12,6 +18,7 @@
    lac u.cdir			" get current working directory
    jms namei; ..		" look up source directory
       jms error			"  not found: return error to user
+#endif
    jms namei; ..		" look up file
       jms error			"  not found: return error
    jms iget			" read file inode
@@ -103,7 +110,11 @@
    dac 1f
    jms arg
    dac 2f
+#ifdef NO_DD
+   lac u.cdir			" Search the current directory
+#else
    lac d4			" Search the directory at i-num 4
+#endif
    jms namei; 0:0		" for the first argument
       jms error			" Didn't find it
    jms namei; 1:0		" In the i-num found by 1st namei,