diff --git a/scans/Makefile b/scans/Makefile
new file mode 100644
index 0000000..2d84114
--- /dev/null
+++ b/scans/Makefile
@@ -0,0 +1,4 @@
+AS7=../tools/as7 -d
+
+system:
+	$(AS7) s?.s > output
diff --git a/scans/Readme b/scans/Readme
index 2a67a55..df3dc80 100644
--- a/scans/Readme
+++ b/scans/Readme
@@ -6,5 +6,12 @@ For modified versions of these files, look in src/cmds and src/sys.
 
 Details of the files:
 
-s1.s: pages 2-3    of 01-s1.pdf, incomplete and with some cruft at the end
+s1.s: pages 2-5    of 01-s1.pdf, incomplete
+s2.s: pages 7-
+s3.s: pages 14-
+s4.s: pages 21-
+s5.s: pages 28-
+s6.s: pages 34-
+sx.s: temp symbol defns (from end of s1.s)
+
 cat.c: pages 21-23 of 06-5-12.pdf
diff --git a/scans/s1.s b/scans/s1.s
index 355c501..d9e639e 100644
--- a/scans/s1.s
+++ b/scans/s1.s
@@ -102,31 +102,94 @@ swap: 0
    dac u.ulistp i
    ion
    jmp dskswap; 07000
+   lac u.dspbuf
+   sna
+   jmp 2f
+   law dspbuf
+   jms movdsp
+2:
+   iof
+   lac o600000
+   tad 9f+t i
+   dac 9f+t i
+   ion
+   jms dskswap; 06000
+   lac u.swapret
+   dac swap
+   lac o20
+   dac maxquant
+   lac u.dspbuf
+   sza
+"** 01-s1.pdf page 4
+   jms movdsp
+3:
+   dzm uquant
+   iof
+   jmp swap i
+t = t+1
 
-" For now, this stuff is defined so that
-" the assembler doesn't complain about it
+swp:
+   jmp .
+   .save; .getuid; .open; .read; .write; .creat; .seek; .tell
+   .close; .link; .unlink; .setuid; .rename; .exit; .time; .intrp
+   .chdir; .chmod; .chown; badcal; .sysloc; badcal; .capt; .rele
+   .status; badcal; .sems; .rmes; .fork
+swn:
+    .-swp-1 i
 
+.intrp:
+   lac u.ac
+   dac u.intflg
+   jmp okexit
+
+.sysloc:
+   lac u.ac
+   and o1777
+   jms betwen; d1; locn
+      jms error
+   tad locsw
+   dac .+1
+   lac ..
+   dac u.ac
+   jmp sysexit
+
+locsw:
+   lac .
+   iget; inode; userdata; sysdata; copy; copyz; betwen; dskrd
+   dskwr; dskbuf; dpdata; namei; pbsflgs; alloc; free; dspdata
+   crdata
+locn:
+   .-locsw-1
 
-pibreak: 23
-u.ac: 100
-u.mq: 3
-u.rq: 3
-copy: 7
-.savblk: 0
-.insys: 0
-uquant: 0
-betwen: 0
-maxquant: 0
-laci: 0
-swp: 0
-badcal: 0
-coldentry: 0
-halt: 0
-dskio: 0
-sysdata: 0
-dskbuf: 0
-o7000: 07000
-o20001: 020001
 chkint: 0
-.save: 0
-lookfor: 0
+   lac .insys
+   sza
+   jmp chkint i
+   lac .int1
+   sna
+   jmp 1f
+   sad u.ofiles+2
+   jmp 2f
+1:
+   lac .int2
+   sna
+   jmp chkint i
+   sad chkint i
+   sad u.ofiles+2
+   skp
+   jmp chkint i
+   dzm .int2
+   jmp 1f
+2:
+   dzm .int1
+1:
+"** 01-s1.pdf page 5
+   lac u.intflg
+   sza
+   jmp chkint i
+   -1
+   dac .insys
+   ion
+   isz chkint
+   jmp chkint i
+
diff --git a/scans/s5.s b/scans/s5.s
index 3baf07f..0d20930 100644
--- a/scans/s5.s
+++ b/scans/s5.s
@@ -2,15 +2,15 @@
 " s5
 
 dskswap: 0
-   cli; ais 3
+   cll; als 3
    dac 9f+t
    jms dsktrans; -64; userdata; 9f+t; dskswap
-   lac 0f+t
+   lac 9f+t
    tad o20
    dac 9f+t
-   jms dsktrans; -4096; 4096; 9f+t; dekswap
-   isc dskswap
-   jmp dskswap
+   jms dsktrans; -4096; 4096; 9f+t; dskswap
+   isz dskswap
+   jmp dskswap i
 
 t = t+1
 
@@ -21,7 +21,7 @@ access: 0
    spa
    jmp access i
    sad i.uid
-   ird 2
+   lrs 2
    lacq
    and mode
    sza
@@ -60,8 +60,8 @@ t = t+1
 fget: 0
    jms betwen; d0; d9
       jmp fget i
-   cli; mul; 3
-   iacq             "** ??
+   cll; mul; 3
+   lacq
 "** 01-s1.pdf page 29
 
    tad ofilesp
@@ -83,14 +83,14 @@ forall: 0
    sad u.limit
    jmp 1f
    lac u.base
-   rai
+   ral
    lac u.base i
-   sni
+   snl
    lrs 9
    and o777
    jmp forall i
 1:
-   lac u.ount
+   lac u.count
    dac u.ac
    jmp sysexit
 
@@ -157,7 +157,7 @@ icreat: 0
    lac u.uid
    dac u.uid
    -1
-   dac i.niks
+   dac i.nlks
    dzm i.size
    jms copyz; i.dskps; 7
    jms iput
@@ -171,9 +171,9 @@ dspput: 0
    jmp i dspput
    sad o14
    jmp 1f
-   img		"** ???
+   lmq
    sad o12
-   jmp dspni
+   jmp dspnl
    lac dsploc i
    sad o400000
    jmp dspleft
@@ -195,19 +195,19 @@ dspleft:
    dac 8
    lac o400000
    dac 8 i
-   cla; liss 18+7
+   cla; llss 18+7
    dac dsploc i
    jmp dspput i
 
-dspni: 0
-   lac dspino
+dspnl: 0
+   lac dsplno
    sad d33
    jmp 1f
-   isz dspino
-   jmp dspni i
+   isz dsplno
+   jmp dspnl i
 1:
    lac o2000
-   wbi
+   wbi			"** ??
    isz dspput
    jmp dspput i
 
@@ -216,12 +216,12 @@ dspinit: 0
    dac dsploc
    lac o300000
    dac dspbuf+3
-   dzm dspino
+   dzm dsplno
    jmp dspinit i
 
 movdsp: 0
    iof
-   cdf
+   caf
    dac dspbufp
    -1
    dac .dspb
@@ -237,7 +237,7 @@ argname: 0
    jms arg
    dac .+2
    jms copy; ..; name; 4
-   lac u.edir
+   lac u.cdir
    jms namei; name
       jms error
    jmp argname i
diff --git a/scans/s6.s b/scans/s6.s
index 9f6559d..e3855c8 100644
--- a/scans/s6.s
+++ b/scans/s6.s
@@ -37,7 +37,7 @@ itrunc: 0
    jmp 1b
    lac i.flags
    and o577777
-   dac i.flacs
+   dac i.flags
    jmp itrunc i
 t = t+4
 
@@ -54,7 +54,7 @@ namei: 0
    -8
    tad i.size
    cma
-   irss 3
+   lrss 3
    dac 9f+t
    sna
    jmp namei i
@@ -94,13 +94,13 @@ t = t+2
 
 iget: 0
    dac ii
-   cli; idiv; 5
+   cll; idiv; 5
    dac 9f+t
    tad d2
    dac 9f+i+1
    jms dskrd
    lac 9f+t
-   cli; mul; 12
+   cll; mul; 12
    lacq
    tad dskbufp
    dac 9f+t
@@ -151,14 +151,14 @@ dget: 0
    alss 3
    dac 9f+t
    jms pget
-   fac 9f+t+1
+   dac 9f+t+1
    jms dskrd
    lac 9f+t
    and o77
    tad dskbufp
    dac 9f+t+2
    dac .+2
-   jms copy; ..; dnode; 8
+   jms copy; ..; inode; 8
    lac 9f+t
    tad d8
    jms betwen; d0; i.size
@@ -173,7 +173,7 @@ dput: 0
    jms dskrd
    lac 9f+t+2
    dac .+3
-   jms copy; dnode; ..; 8
+   jms copy; inode; ..; 8
    lac 9f+t+1
    jms dskwr
    jmp dput i
@@ -181,11 +181,11 @@ dput: 0
 t = t+3	"** first t not there (hole from hole punch?)
 
 pget: 0
-   irss 6
+   lrss 6
    dac 9f+t
    lac i.flags
 
-"** 01-s1.pdf page 36
+"** 01-s1.pdf page 37
 
    and o200000
    sza
@@ -193,7 +193,7 @@ pget: 0
    lac 9f+t
    jms betwen; d0; d6
       jmp 1f
-   rad idskpp
+   tad idskpp
    dac 9f+t
    lac 9f+t i
    sna
@@ -203,8 +203,8 @@ pget: 0
 1:
    jms alloc
    dac 9f+t+1
-   jms copy; idskps; dskbuf; 7
-   jms copyz; dskbuf+7; 6467	"** NUMBER UNCLEAR 64-7???
+   jms copy; i.dskps; dskbuf; 7
+   jms copyz; dskbuf+7; 64-7	"** NUMBER UNCLEAR
    lac 9f+t+1
    jms dskwr
    lac 9f+t+1
@@ -247,8 +247,8 @@ iwrite: 0
 
 "** 01-s1.pdf page 38
 
-   dac oread
-   lac cslp
+   dac iread
+   lac cskp
    dac iwrite
    jmp 1f
 
@@ -282,7 +282,7 @@ iread: 0
 1:
    lac 9f+t
    jms pget
-   das 9f+t+3
+   dac 9f+t+3
    jms dskrd
    lac 9f+t
    and o77
@@ -331,7 +331,7 @@ finac: 0
    sma
    jms error
    lac f.i
-   jms ihet
+   jms iget
    jms finac i
 
 dacisize: 0
diff --git a/scans/s7.s b/scans/s7.s
index 224f223..42d841e 100644
--- a/scans/s7.s
+++ b/scans/s7.s
@@ -3,20 +3,20 @@
 
 pibreak:
    dac .ac	"** CROSSED OUT....
-   dpsf
+   lpsf
    jmp 1f
 
-   dpcf
-   dprs
+   lpcf
+   dprs		"** ??
    dac dpstat
-   sma rad
+   sma ral
    jmp 2f
-   dprc
+   dprc		"** ??
    dac dpchar
    -1
    dac dpread
    lac dpstat
-   rai
+   ral
 2:
    sma
    jmp piret
@@ -28,7 +28,7 @@ pibreak:
    jmp 1f
 
    lpb
-   dac pbsfigs
+   dac pbsflgs
    isz s.tim+1
    skp
    isz s.tim
@@ -251,7 +251,7 @@ ttyrestart: 0
    lpb
    dac pbsflgs+1
 
-"** 01-s1.pdf page 44
+"** 01-s1.pdf page 45
 
    and o2000
    sna
diff --git a/scans/s8.s b/scans/s8.s
index a26d3e9..9a243c2 100644
--- a/scans/s8.s
+++ b/scans/s8.s
@@ -102,7 +102,7 @@ q2:
    .+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0
    .+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0;.+2;0
 dsploc: .=.+1
-dspinc: .=.+1
+dsplno: .=.+1
 dspbuf:
    0065057;0147740;0160000
    .=.+30
@@ -113,11 +113,11 @@ coldentry:
    clon
    law 3072
    vcga
-   jsp dspinit
+   jms dspinit
    law dspbuf
-   jsp movdsp
+   jms movdsp
    cla
-   jsp dskio; 06000
+   jms dskio; 06000
    jms copy; dskbuf; sysdata; ulist-sysdata
    lac d3
    jms namei; initf
@@ -194,7 +194,7 @@ inode:
    i.flags: .=.+1
    i.dskps: .=.+7
    i.uid: .=.+1
-   i.lks: .=.+1
+   i.nlks: .=.+1
    i.size: .=.+1
    i.uniq: .=.+1
       .= inode+12
diff --git a/scans/sx.s b/scans/sx.s
new file mode 100644
index 0000000..958bc61
--- /dev/null
+++ b/scans/sx.s
@@ -0,0 +1,22 @@
+
+" For now, this stuff is defined so that
+" the assembler doesn't complain about it
+
+.save: 0
+alloc: 0
+betwen: 0
+chkint: 0
+copy: 7
+copyz: 0
+dskio: 0
+dskrd: 0
+dsktrans: 0
+dskwr: 0
+error: 0
+free: 0
+halt: 0
+laci: 0
+lookfor: 0
+o7000: 07000
+o70000: 070000
+swp: 0
diff --git a/tools/as7 b/tools/as7
index 1d235b0..8cc7226 100755
--- a/tools/as7
+++ b/tools/as7
@@ -21,6 +21,8 @@ my $origline;  # The current input line of code
 
 my $stage = 1; # Pass one or pass two
 my $debug = 0; # Run in debug mode
+my $errors = 0; # set to non-zero on error
+my %Undef;	# undefined symbols: only complain once
 
 ### Main program ###
 
@@ -87,13 +89,25 @@ for my $i ( 0 .. $#Mem ) {
     }
 }
 
-exit(0);
+exit($errors);
+
+my $file;			# global for error messages
+my $lineno;
+
+sub err {
+    my $msg = shift;
+    $errors = 1;		# exit status
+    print STDERR "$file:$lineno: $msg\n";
+    return 0;
+}
 
 # Open and parse the given file
 sub parse_file {
-    my $file = shift;
+    $file = shift;
     open( my $IN, "<", $file ) || die("Cannot read $file: $!\n");
+    $lineno = 0;
     while ( my $line = <$IN> ) {
+	$lineno++;
 
         # Lose the end of line and any leading/trailing whitespace
         # Discard any comments and preceding comment whitespace
@@ -111,12 +125,12 @@ sub parse_file {
             # Split into a section with possible labels and a
             # statement section with definitely no labels. The ?
             # makes the first pattern less greedy.
-            #print("cmd is >$cmd<\n");
+            print("cmd is >$cmd<\n");
             $cmd =~ m{(.*?)([^:]*$)};
             my $labelsect = $1;
             my $statement = $2;
 
-            #print(">$labelsect< >$statement<\n");
+	    #print(">$labelsect< >$statement<\n");
 
             # Split $labelsect into labels using the : character
             my @labellist = split( /:\s*/, $labelsect );
@@ -147,9 +161,9 @@ sub parse_label {
     }
 
     # It's a textual label, check if it's been defined before
-    die("Label $label defined multiple times\n")
-      if ( defined( $Label{$label} ) );
-
+    if ( defined( $Label{$label} ) ) {
+	err("Label $label defined multiple times\n") if ( $stage == 1 );
+    }
     # Otherwise, save its value
     $Label{$label} = $Var{'.'};
     #printf( "Set absolute label %s to 0%o\n", $label, $Label{$label} );
@@ -202,6 +216,7 @@ sub parse_statement {
 sub parse_expression {
     my $expression = shift;
 
+print "exp: $expression\n";
     # If it's a defined variable ( . , .. , etc.)
     # return the value
     return ( $Var{$expression} )
@@ -426,7 +441,11 @@ sub parse_expression {
         #print("Did a subtraction and got $diff\n");
         return ($diff);
     }
-    die("I have no idea what $expression is in pass two\n") if ( $stage == 2 );
+    if ( $stage == 2 ) {
+	err("undefined: $expression") unless (defined $Undef{$expression});
+	$Undef{$expression} = 1;
+    }
+    return 0;
 }
 
 # Add two expression together
@@ -463,18 +482,20 @@ sub find_relative_label {
     my $curlocation = $Var{'.'};
 
     # Error check: no labels at all
-    die("No relative labels\n") if ( !defined( $Rlabel{$label} ) );
+    if ( !defined( $Rlabel{$label} ) ) {
+	return err("relative label $label not defined\n");
+    }
 
     # Get the list of possible locations for this label
     my $locarray = $Rlabel{$label};
 
     # Error check: no locations
-    die("No relative labels\n") if ( @{$locarray} == 0 );
+    return err("No relative labels") if ( @{$locarray} == 0 );
 
     # Error check: forward but no next location, or backward but no previous
-    die("No forward label\n")
+    return err("No forward label $label")
       if ( ( $direction eq 'f' ) && ( $curlocation > $locarray->[-1] ) );
-    die("No backward label\n")
+    return err("No backward label $label")
       if ( ( $direction eq 'b' ) && ( $curlocation < $locarray->[0] ) );
 
     # Search forward for a location larger then the current one