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

build/Makefile

@@ -22,16 +22,29 @@ BINARIES=../binaries/
 
 all: cmd others a.rim image.fs copybinaries
 
+# Make alternative everything: no dd but . and ..
+alt: altcmd altothers alta.rim altimage.fs
+
 # The run rule has no dependencies so that the system can be booted easily
 # and frequently with make run. However, you have to manually make all first!
 run:
 	$(PDP7) unixv0.simh
 
+# Alternative run, use the altimage.fs
+altrun:
+	$(PDP7) altunixv0.simh
+
 # Warm boot Unix kernel: boots into init and a login prompt
 a.rim:
 	$(AS) -f rim  -o a.rim $(SYSSRC)/sop.s $(SYSSRC)/s[1-8].s
 	$(AS) -n -f list -o a.lst $(SYSSRC)/sop.s $(SYSSRC)/s[1-8].s
 
+# Alternative kernel: no dd, but . and ..
+alta.rim:
+	$(AS) -f rim -o alta.rim -DNO_DD $(SYSSRC)/sop.s $(SYSSRC)/s[1-8].s
+	$(AS) -n -f list -o alta.lst -DNO_DD $(SYSSRC)/sop.s $(SYSSRC)/s[1-8].s
+
+
 # Cold boot Unix kernel: attempts to build a minimal filesystem.
 # Don't use this one!
 coldboot:
@@ -40,16 +53,22 @@ coldboot:
 
 # Filesystem image
 image.fs: cmd others
-	$(MKFS) --format simh proto
+	$(MKFS) proto
 	$(FSCK) image.fs
 
+# Alternate filesystem image: . and .. but no dd
+altimage.fs: altcmd altothers
+	$(MKFS) -1 -2 -3 -o altimage.fs altproto
+	$(FSCK) -3 altimage.fs
+
+
 copybinaries:
 	mkdir -p $(BINARIES)
 	cp image.fs $(BINARIES)
 	cp a.rim $(BINARIES)
 
 clean:
-	rm -f a.rim image.fs a.lst n.out
+	rm -f a.rim image.fs a.lst n.out altimage.fs alta.rim alta.lst
 	rm -rf $(BINDIR)
 	rm -rf $(TESTDIR)
 	rm -rf $(BINARIES)
@@ -62,6 +81,11 @@ cmd: dirs $(BINDIR)/as $(BINDIR)/cat $(BINDIR)/check $(BINDIR)/chmod \
 	$(BINDIR)/chown $(BINDIR)/chrm $(BINDIR)/cp $(BINDIR)/ds $(BINDIR)/ed \
 	$(BINDIR)/init
 
+# Alternate commands: no dd, but . and ..
+altcmd: dirs $(BINDIR)/as $(BINDIR)/cat $(BINDIR)/check $(BINDIR)/chmod \
+	$(BINDIR)/chown $(BINDIR)/altchrm $(BINDIR)/cp $(BINDIR)/ds $(BINDIR)/ed \
+	$(BINDIR)/altinit
+
 $(BINDIR)/as: $(CMDSRC)/as.s
 	$(AS) $(ASARGS) -o $(BINDIR)/as $(CMDSRC)/as.s
 
@@ -80,6 +104,9 @@ $(BINDIR)/chown: $(CMDSRC)/chown.s
 $(BINDIR)/chrm: $(CMDSRC)/chrm.s
 	$(AS) $(ASARGS) -o $(BINDIR)/chrm $(CMDSRC)/chrm.s
 
+$(BINDIR)/altchrm: $(OTHERSRC)/wktchrm.s
+	$(AS) $(ASARGS) -o $(BINDIR)/altchrm -DNO_DD $(OTHERSRC)/wktchrm.s
+
 $(BINDIR)/cp: $(CMDSRC)/cp.s
 	$(AS) $(ASARGS) -o $(BINDIR)/cp $(CMDSRC)/cp.s
 
@@ -92,10 +119,19 @@ $(BINDIR)/ed: $(CMDSRC)/ed1.s $(CMDSRC)/ed2.s
 $(BINDIR)/init: $(CMDSRC)/init.s
 	$(AS) $(ASARGS) -o $(BINDIR)/init $(CMDSRC)/init.s
 
+# Alternative init: no dd directory
+$(BINDIR)/altinit: $(CMDSRC)/init.s
+	$(AS) $(ASARGS) -DNO_DD -o $(BINDIR)/altinit $(CMDSRC)/init.s
+
 # The commands that did not come from the scans
 others: dirs $(BINDIR)/sh $(BINDIR)/wktcat $(BINDIR)/wktcp $(BINDIR)/date \
 	$(BINDIR)/ln $(BINDIR)/ls $(BINDIR)/mv $(BINDIR)/stat
 
+# Alternative other commands: no dd, but . and ..
+altothers: dirs $(BINDIR)/sh $(BINDIR)/wktcat $(BINDIR)/wktcp $(BINDIR)/date \
+	$(BINDIR)/ln $(BINDIR)/altls $(BINDIR)/mv $(BINDIR)/stat
+
+
 $(BINDIR)/sh: $(OTHERSRC)/pbsh.s
 	$(AS) $(ASARGS) -o $(BINDIR)/sh $(OTHERSRC)/pbsh.s
 
@@ -114,6 +150,9 @@ $(BINDIR)/ln: $(OTHERSRC)/wktln.s
 $(BINDIR)/ls: $(OTHERSRC)/wktls.s
 	$(AS) $(ASARGS) -o $(BINDIR)/ls $(OTHERSRC)/wktls.s
 
+$(BINDIR)/altls: $(OTHERSRC)/wktls.s
+	$(AS) $(ASARGS) -o $(BINDIR)/altls -DNO_DD $(OTHERSRC)/wktls.s
+
 $(BINDIR)/mv: $(OTHERSRC)/wktmv.s
 	$(AS) $(ASARGS) -o $(BINDIR)/mv $(OTHERSRC)/wktmv.s
 

build/altproto

@@ -0,0 +1,47 @@
+# Alternative prototype file for PDP-7 Unix filesystem layout
+#
+# This one has . and .. but no dd directory entries
+#
+# Entries are one of:
+#    filename f[r-][w-][r-][w-] uid local_file_to_insert
+#    dirname  d[r-][w-][r-][w-] uid [inumber]
+#    device   i[r-][w-][r-][w-] uid inumber
+#    link     l---- inumber
+#
+# The top directory's name is ignored
+# Numeric values are in decimal
+# Contents of each directory ends with a $ on a line by itself
+# Format was inspired by 6th Edition mkfs
+#
+/ 	         drwr- -1 2
+    system       drwr- -1 3
+        ttyin    irwr- -1 6
+        keyboard irwr- -1 7
+        pptin    irwr- -1 8
+        ttyout   irwr- -1 11
+        display  irwr- -1 12
+        pptout   irwr- -1 13
+        as       frwr- -1 bin/as
+        cat      frwr- -1 bin/cat
+        chmod    frwr- -1 bin/chmod
+        chown    frwr- -1 bin/chown
+        chrm     frwr- -1 bin/altchrm
+        cp       frwr- -1 bin/cp
+        date     frwr- -1 bin/date
+        ds       frwr- -1 bin/ds
+        ed       frwr- -1 bin/ed
+	init     frwr- -1 bin/altinit
+        ln       frwr- -1 bin/ln
+        ls       frwr- -1 bin/altls
+        mv       frwr- -1 bin/mv
+	password frw-- -1 fs/password
+        sh       frwr- -1 bin/sh
+        stat     frwr- -1 bin/stat
+	$
+    ken      drwr- 10
+      system l----  3
+        hello     frwr- 10 fs/hello
+      $
+    dmr      drwr- 12
+      system l----  3
+      $

build/altunixv0.simh

@@ -0,0 +1,12 @@
+set cpu 8k
+set cpu eae
+set cpu history=100
+show cpu
+
+set tti unix
+set rb ena
+att rb altimage.fs
+show dev
+
+load -S alta.rim
+dep pc 0100

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
+#ifdef NO_DD
-   sys chdir; dir
+   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,

tools/fsck7

@@ -57,7 +57,7 @@ use constant D_UNIQ     => 5;
 use constant D_NUMWORDS => 8;      # Eight words in a direntry
 
 # Globals
-my $debug = 0;
+my ($debug, $no_dd) = (0,0);
 my @Block;                         # Array of blocks and words in each block
 my @Freelist;                      # List of free block numbers
 my @Usedlist;                      # List of in-use block numbers
@@ -271,7 +271,10 @@ sub usage {
 
 ### MAIN PROGRAM
 
-GetOptions( 'debug|d' => \$debug, )
+GetOptions(
+	'debug|d' => \$debug,
+	'no_dd|3' => \$no_dd,
+)
   or usage();
 
 usage() if ( @ARGV < 1 );
@@ -327,6 +330,10 @@ foreach my $inode ( 0 .. NUMINODEBLKS * INODESPERBLK - 1 ) {
 }
 
 # Now check the directories. We start with dd at i-num 4.
-check_directory( 4, "dd" );
+if ($no_dd) {
+  check_directory( 2, "" );
+} else {
+  check_directory( 4, "dd" );
+}
 
 exit(0);

tools/mkfs7

@@ -55,7 +55,7 @@ use constant D_UNIQ     => 5;
 use constant D_NUMWORDS => 8;    # Eight words in a direntry
 
 # Globals
-my ($debug,$wantdot,$wantdotdot)=(0,0,0);
+my ($debug,$wantdot,$wantdotdot, $no_dd)=(0,0,0,0);
 my @Block;	# Array of blocks and words in each block
 my @Freelist;	# List of free block numbers
 my $nextinum   = 1;	# i-num 0 is never used
@@ -353,9 +353,11 @@ sub make_dir {
     }
 
     # Finally, add a "dd" entry to this directory. We get the
-    # i-num from the first entry in the Dirstack
+    # i-num from the first entry in the Dirstack. Sorry for the dbl negative.
-    add_direntry( "dd", $Dirstack[0]->[2] );
+    if (!$no_dd) {
-    dprintf("Added a dd entry to i-num %d\n", $Dirstack[0]->[2] );
+      add_direntry( "dd", $Dirstack[0]->[2] );
+      dprintf("Added a dd entry to i-num %d\n", $Dirstack[0]->[2] );
+    }
 
     dprintf( "Made directory %s perms %06o uid %d in inum %d\n\n",
         $dirname, $perms, $uid, $inum );
@@ -643,6 +645,7 @@ GetOptions(
     'debug|d'    => \$debug,
     'dot|1'      => \$wantdot,
     'dotdot|2'   => \$wantdotdot,
+    'no_dd|3'    => \$no_dd,
     'format|f=s' => \$format,
     'output|o=s' => \$output,
 ) or usage();