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 9b10af2..db3bca8 100644
--- a/src/sys/s2.s
+++ b/src/sys/s2.s
@@ -29,14 +29,14 @@
 .capt:
    lac u.ac			" get user AC
    dac u.dspbuf			" save as user display buffer
-   jms movdsp
+   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/s7.s b/src/sys/s7.s
index ce52456..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
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