diff --git a/src/other/pbsh.s b/src/other/pbsh.s
index b723481..1bb0038 100644
--- a/src/other/pbsh.s
+++ b/src/other/pbsh.s
@@ -280,11 +280,15 @@ parent:
 "	try to read any messages) the shell's blocked smes call returned an
 "	error indication that the target process did not exist. Thus the
 "	shell's smes became, in effect, the equivalent of wait.
-   dac pid
-   lac delimchar
+"
+"	PLB: The "exit" system call code apears to "fall" into the
+"	rmes code So Dennis' memory of what the shell did may have
+"	been correct, but not for the reason he remembered.
+   dac pid			" save child pid
+   lac delimchar		" get command delimiter
    sad o46			" ampersand?
     jmp newcom			"  yes: go back without wait
-   lac pid
+   lac pid			" no: get pid
    sys smes			" hang until child exits
 2: lac delimchar
    sad o73			" semi?
diff --git a/src/sys/s1.s b/src/sys/s1.s
index 27ed5e3..a7a07ab 100644
--- a/src/sys/s1.s
+++ b/src/sys/s1.s
@@ -107,7 +107,7 @@ swap: 0
    lac u.dspbuf
    sna				" process using display??
    jmp 2f			"  no
-   law dspbuf
+   law dspbuf			" reset to default display buffer
    jms movdsp
 2:
    iof				" disable interrupts
@@ -123,7 +123,7 @@ swap: 0
    lac u.dspbuf
    sza				" using display?
 "** 01-s1.pdf page 4
-   jms movdsp			"  yes.
+   jms movdsp			"  yes. switch to user display bufferx
 3:
    dzm uquant			" no. reset process tick count
    iof
diff --git a/src/sys/s2.s b/src/sys/s2.s
index b0eb48a..db3bca8 100644
--- a/src/sys/s2.s
+++ b/src/sys/s2.s
@@ -27,16 +27,16 @@
 
 	" capture display?
 .capt:
-   lac u.ac
-   dac u.dspbuf
-   jms movdsp
+   lac u.ac			" get user AC
+   dac u.dspbuf			" save as user display buffer
+   jms movdsp			" switch to user display buffer
    jmp sysexit
 
 	" release display?
 .rele:
-   dzm u.dspbuf
-   law dspbuf
-   jms movdsp
+   dzm u.dspbuf			" clear user display buffer pointer
+   law dspbuf			" get default display buffer
+   jms movdsp			" change to it
    jmp sysexit
 
 .chmod:
diff --git a/src/sys/s3.s b/src/sys/s3.s
index d2b25da..c686a6e 100644
--- a/src/sys/s3.s
+++ b/src/sys/s3.s
@@ -104,7 +104,7 @@ badcal:				" bad (unimplemented) system call
    lac u.dspbuf
    sna				" process using display?
    jmp .+3			"  no
-   law dspbuf			"   yes
+   law dspbuf			"   yes: get default display buffer
    jms movdsp			"   move display
    jms awake
    lac u.ulistp i
diff --git a/src/sys/s5.s b/src/sys/s5.s
index 3520ef0..a0a7b4b 100644
--- a/src/sys/s5.s
+++ b/src/sys/s5.s
@@ -242,11 +242,13 @@ dspnl: 0			" only called once!
 dspinit: 0
    lac dspbufp3			" get pointer to dspbuf+3
    dac dsploc			" store location
-   lac o400000			" display "TRAP" instruction
+   lac o400000			" display "TRAP" instruction (end of list)
    dac dspbuf+3			" save in buffer
    dzm dsplno			" clear display line number
    jmp dspinit i
 
+	" "move display" (change display buffer pointer)
+	" called with new buffer pointer in AC??
 movdsp: 0
    iof
    cdf
diff --git a/src/sys/s7.s b/src/sys/s7.s
index f175a46..236c288 100644
--- a/src/sys/s7.s
+++ b/src/sys/s7.s
@@ -80,7 +80,7 @@ cnop:			" fetched as constant in iread
 1: lds				" load display status (see 03-scope.pdf pg 25)
    sma ral			" edges flag??
    jmp 1f			"  not set
-   cdf				" clear display flags?
+   cdf				" clear display flags
    lac .dspb
    sna
    jmp piret
@@ -101,7 +101,7 @@ dsprestart:
 
 1: sna ral			" dataphone flag set (bit 7)??
    jmp .+3			"  no
-   raef				" XXX: fix comment
+   raef				" "resume after edges flag"
    jmp piret			" return
    sma				" light pen flags (bit 2)
    jmp 1f			"  no
@@ -114,9 +114,9 @@ dsprestart:
 1: ksf				" (TTY) keyboard flag set?
    jmp 1f			"  no
 
-   lac ttydelay		" get TTY delay
-   sma				"
-   isz ttydelay
+   lac ttydelay			" get TTY delay
+   sma				" minus (waiting for output)?
+   isz ttydelay			"  no: increment??? (make more positive)
    krb				" read keyboard buffer
    dac char			" save in char
    sad o375			" interrupt char (TTY ALT MODE?)
@@ -128,12 +128,12 @@ dsprestart:
    jms wakeup			" wake processes
    dac sfiles+0			" clear sleep word
    lac char			" get character
-   sad o212			" odd condition (break???)
+   sad o212			" new line (with parity)??
    skp				"  yes
    jmp piret			"   no: done
-   lac sfiles+1			" get ttyout wait word
-   sma				" bit for process 1 already set?
-   xor o400000			" no, make it so
+   lac sfiles+1			" get ttyout sleep word
+   sma				" highest bit set?
+   xor o400000			" no, make it so (why???)
    dac sfiles+1			" save back
 
 "** 01-s1.pdf page 43
@@ -259,7 +259,7 @@ ttyrestart: 0
    jmp piret
 
 		"** BEGIN CROSSED OUT
-1: spb					" graphic 2 push button flag set?
+1: spb					" any graphic-2 push button?
    jmp 1f				"  no
 
    cpb					" clear push button flag
@@ -268,11 +268,11 @@ ttyrestart: 0
 
 "** 01-s1.pdf page 45
 
-   and o2000
-   sna
-   jmp piret
-   jms dspinit
-   lac sfiles+6
+   and o2000				" get push button 7
+   sna					" set?
+   jmp piret				"  no: done
+   jms dspinit				" yes: reset display buffer
+   lac sfiles+6				" wake up anyone sleeping on display
    jms wakeup
    dac sfiles+6
    cla					" clear button lights
diff --git a/src/sys/s8.s b/src/sys/s8.s
index 4aaff44..5d86d3f 100644
--- a/src/sys/s8.s
+++ b/src/sys/s8.s
@@ -125,7 +125,7 @@ coldentry:
    law 3072			" initialize display....
    wcga
    jms dspinit
-   law dspbuf
+   law dspbuf			" set display buffer to default
    jms movdsp
    cla				" read system block from disk
    jms dskio; 06000