diff --git a/tar.tal b/tar.tal
index e306951..c9a022a 100644
--- a/tar.tal
+++ b/tar.tal
@@ -2,12 +2,18 @@
 ( )
 ( by d_m )
 ( )
-( currently only supports listing the contents of tar files )
-( )
 ( see https://en.wikipedia.org/wiki/Tar_(computing)#UStar_format )
+( )
+( TODO: )
+( - support creating archives )
+( - arg validation should depend on mode )
+( - validate checksums )
+( - better error messages on unsupported files, e.g. symlinks )
+( - better usage message )
+( - support using "-" for stdin/stdout? )
 
-( File1 is used to read the tar file )
-( TODO File2 is used to write files and directories )
+( File1 is used to read/write the tar file )
+( File2 is used to read/write files and directories )
 |a0 @File1 [ &vec $2 &ok $2 &stat $2 &del $1 &append $1 &name $2 &len $2 &r $2 &w $2 ]
 |b0 @File2 [ &vec $2 &ok $2 &stat $2 &del $1 &append $1 &name $2 &len $2 &r $2 &w $2 ]
 
@@ -132,7 +138,7 @@
 @sanitize-path ( s* -> s1* )
     LDAk LIT "/ NEQ JMP INC2 JMP2r
 
-@extra-xyz ( n* -> extra* )
+@remainder-512 ( n* -> extra* )
     #01ff AND2 #0200 SWP2 SUB2 ORAk ?{ POP2 #0000 } JMP2r
 
 @expand-file ( type^ -> )
@@ -141,7 +147,7 @@
     DUP2 #0064 lprint #0a18 DEO
     .File2/name DEO2
     ;header/size load-octal11 STH2k write
-    STH2r extra-xyz skip-lo !expand-entries
+    STH2r remainder-512 skip-lo !expand-entries
 
 @expand-dir ( type^ -> )
     POP
@@ -149,53 +155,9 @@
     DUP2 #0064 lprint #0a18 DEO
     .File2/name DEO2
     #0004 .File2/len DEO2
-    ;tmp .File2/w DEO2
+    #0001 .File2/w DEO2
     !expand-entries
 
-@tmp "tmp 0a 00
-
-( TODO write data from memory into the tar file )
-@z-write-memory ( filename* size* data* -> )
-    STH2 STH2k z-write-file-header ( [data* size*] )
-    STH2r STH2r z-write-file-body JMP2r ( )
-    .File1/len
-
-( TODO write out the file header )
-@z-write-file-header ( filename* size* -> )
-    SWP2 ;header/filename copy JMP2r
-    z-write-size-2
-    ( TODO: compute checksum )
-    LIT "0 ;header/type STA
-    #00 ;header/linkname STA
-    JMP2r
-
-( TODO write file body into archive )
-@z-write-file-body ( size* data* -> )
-    SWP2 .File1/len DEO2 .File1/w DEO2 JMP2r
-
-( TODO write file size, limited to 64k )
-@z-write-size-2 ( size* -> )
-    ;header/size STH2             ( size* [start*] )
-    LIT2r 000a ADD2r              ( size* [start* last*] )
-    &loop                         ( size* [start* pos*] )
-        LTH2kr STHr ?&done        ( size* [start* pos*] )
-        DUP2 #0007 AND2           ( size* size%8* [start* pos*] )
-        NIP LIT "0 ADD            ( size* octal^ [start* pos*] )
-        STH2kr STA                ( size* [start* pos*] )
-        #03 SFT2                  ( size/8* [start* pos*] )
-        LIT2 0001 SUB2 !&loop     ( size/8* [start* pos-1*] )
-    &done                         ( zero* [start* pos*] )
-        POP2 POP2r POP2r JMP2r    ( )
-
-( TODO: copy string from src to dst )
-( TODO: need a length param too )
-@copy ( src* dst* -> )
-    STH2
-    &loop
-        LDAk DUP STH2kr STA2 ?&ok
-        POP2 POP2r JMP2r
-    &ok INC2 INC2r !&loop
-
 ( writes `n` bytes from File1 to File2 )
 ( uses a 32k internal buffer )
 @write ( carry^ hi* lo* -> )
@@ -407,7 +369,7 @@
     JMP2r
 
 ( some handy string constants )
-@usage "usage: 20 "uxncli 20 "tar.rom 20 "c|t|x 20 "FILENAME 0a 00
+@usage "usage: 20 "uxncli 20 "tar.rom 20 "t|x 20 "FILENAME 0a 00
 @missing-mode "error: 20 "missing 20 "mode 0a 00
 @missing-filename "error: 20 "missing 20 "filename 0a 00
 @too-many-arguments "error: 20 "too 20 "many 20 "arguments 0a 00