system comments

src/sys/s1.s

@@ -64,9 +64,9 @@ sysexit:			" common system call exit code
    jms dskio; 07000		" save to disk?
 1:
    dzm .insys			" clear "in system call" flag
-   jms chkint
-      skp
-   jmp .save			" dump core??
+   jms chkint			" pending interrupt?
+      skp			"  no
+   jmp .save			"   yes: dump core
    jms copy; u.rq+2; 10; 6	" restore auto-index locations 10-15
    lac u.rq+1			" restore auto-index location 9
    dac 9
@@ -139,12 +139,18 @@ swp:			" system call dispatch table
 swn:
    .-swp-1 i		" count of system calls, plus indirect!
 
+	" AC/ new value for intflg
+	"   sys intrp
 .intrp:
    lac u.ac
    dac u.intflg
    jmp okexit
 
-.sysloc:		" "sysloc": syscall to return system addresses
+	" syscall to retrieve system addresses (data & routines!!)
+	" AC/ index (1..17)
+	"   sys sysloc
+	" AC/ address (or -1 on bad index)
+.sysloc:
    lac u.ac
    and o17777
    jms betwen; d1; locn
@@ -155,7 +161,7 @@ swn:
    dac u.ac
    jmp sysexit
 
-locsw:			" table of system data structures for "sysloc" call
+locsw:			" table of system addresses for sysloc
    lac .
    iget; inode; userdata; sysdata; copy; copyz; betwen; dskrd
    dskwr; dskbuf; dpdata; namei; pbsflgs; alloc; free; dspdata
@@ -163,34 +169,41 @@ locsw:			" table of system data structures for "sysloc" call
 locn:
    .-locsw-1
 
+	" check if interrupt for user
+	" checks .int1 and .int2 (contain i-number of interrupt source)
+	" call:
+	" .insys/ 0
+	"   jms chkint
+	"    no: no interrupt, or intflg set (discards interupt)
+	"   yes: PI off, .insys set
 chkint: 0
    lac .insys
-   sza
-   jmp chkint i
-   lac .int1
-   sna
-   jmp 1f
-   sad u.ofiles+2
-   jmp 2f
+   sza				" in system?
+   jmp chkint i			"  yes: return
+   lac .int1			" get inumber of interrupt1 source?
+   sna				" zero?
+   jmp 1f			"  yes: skip stdin check
+   sad u.ofiles+2		" non-zero: compare to stdin inumber
+   jmp 2f			"  same
 1:
-   lac .int2
-   sna
-   jmp chkint i
-   sad u.ofiles+2
-   skp
-   jmp chkint i
-   dzm .int2
+   lac .int2			" get inum of interrupt 2 source?
+   sna				" zero?
+   jmp chkint i			"  yes: return
+   sad u.ofiles+2		" non-zero: compare to stdin inumber
+   skp				"  match!
+   jmp chkint i			"   no match: return
+   dzm .int2			" clear int2 source
    jmp 1f
 2:
-   dzm .int1
+   dzm .int1			" clear int1 source
 1:
 "** 01-s1.pdf page 5
-   lac u.intflg
-   sza
-   jmp chkint i
+   lac u.intflg			" get user intflg
+   sza				" zero?
+   jmp chkint i			"  no: ignore
    -1
-   dac .insys
-   ion
-   isz chkint
+   dac .insys			" set "in system" flag
+   ion				" enable interrupts
+   isz chkint			" give skip return
    jmp chkint i