diff --git a/blk/000 b/blk/000
index 2bb121c..af5a917 100644
--- a/blk/000
+++ b/blk/000
@@ -3,7 +3,8 @@ Collapse OS file system
 This is a Forth-style filesystems which is very simple. It is a
 list of 1024 bytes block, organised in 16 lines of 64 columns
 each. You refer to blocks by numbers. You show them with LIST.
-You interpret them with LOAD.
+You interpret them with LOAD. For a convenient way to browse
+blocks, see Block Explorer at B100.
 
 Conventions: When you see "(cont.)" at the bottom right of a
 block, it means that the next block continues the same kind of
diff --git a/blk/100 b/blk/100
index 8680085..32059f1 100644
--- a/blk/100
+++ b/blk/100
@@ -7,4 +7,4 @@ USAGE: When loaded, the Forth interpreter is replaced by the
 explorer interpreter. Typing "Q" quits the program.
 
 Typing a decimal number followed by space or return lists the
-contents of that block.
+contents of that block. B for previous block, N for next.
diff --git a/blk/102 b/blk/102
index 6e9ec68..aa7598f 100644
--- a/blk/102
+++ b/blk/102
@@ -1,2 +1,14 @@
-: foo ." Hello world! " 42 . ;
-foo
+103 LOAD
+VARIABLE _K
+
+: PGM
+    100 _LIST
+    BEGIN
+        KEY
+        DUP 'Q' = IF DROP EXIT THEN
+        DUP 58 ( '9'+1 ) < IF _NUM
+        ELSE
+            _K ! _K (find) IF EXECUTE THEN
+        THEN
+    AGAIN
+; PGM
diff --git a/blk/103 b/blk/103
index 2d94bff..d99ee77 100644
--- a/blk/103
+++ b/blk/103
@@ -1 +1,9 @@
-42 . 102 LOAD 43 .
+VARIABLE ACC
+: _LIST ." Block " DUP . CRLF LIST ;
+: _NUM
+    ACC @ SWAP _pdacc
+    IF _LIST 0 THEN
+    ACC !
+;
+: B BLK> @ 1- DUP BLK> ! _LIST ;
+: N BLK> @ 1+ DUP BLK> ! _LIST ;