From 08111952124d48f4402ca2228f7d004ec67bb788 Mon Sep 17 00:00:00 2001
From: Tom Everett <tom@khubla.com>
Date: Sat, 5 Mar 2016 15:21:44 -0700
Subject: [PATCH] added existing pdp7 files that parse properly

---
 .../com/khubla/pdp7parse/antlr4/pdp7.g4       |   17 +-
 pdp7parse/src/test/resources/as.s             | 1025 +++++++++++++++++
 pdp7parse/src/test/resources/bc.s             |  288 +++++
 pdp7parse/src/test/resources/bi.s             |  433 +++++++
 pdp7parse/src/test/resources/s1.s             |  130 ++-
 pdp7parse/src/test/resources/s2.s             |  177 +--
 pdp7parse/src/test/resources/s3.s             |  184 +--
 pdp7parse/src/test/resources/s4.s             |  371 ++++++
 pdp7parse/src/test/resources/s5.s             |  109 +-
 pdp7parse/src/test/resources/s6.s             |  221 ++--
 pdp7parse/src/test/resources/s7.s             |  372 ++++++
 pdp7parse/src/test/resources/s8.s             |  134 ++-
 12 files changed, 3027 insertions(+), 434 deletions(-)
 create mode 100644 pdp7parse/src/test/resources/as.s
 create mode 100644 pdp7parse/src/test/resources/bc.s
 create mode 100644 pdp7parse/src/test/resources/bi.s
 create mode 100644 pdp7parse/src/test/resources/s4.s
 create mode 100644 pdp7parse/src/test/resources/s7.s

diff --git a/pdp7parse/src/main/antlr4/com/khubla/pdp7parse/antlr4/pdp7.g4 b/pdp7parse/src/main/antlr4/com/khubla/pdp7parse/antlr4/pdp7.g4
index ed5d7b4..f81cc28 100644
--- a/pdp7parse/src/main/antlr4/com/khubla/pdp7parse/antlr4/pdp7.g4
+++ b/pdp7parse/src/main/antlr4/com/khubla/pdp7parse/antlr4/pdp7.g4
@@ -62,9 +62,15 @@ argument
    ;
 
 assignment
-   : (opcode | variable | LOC | RELOC) '=' expression
+   :  symbol '=' expression
    ;
 
+// note that opcodes can be symbols.  This is because it is legal to have a 
+// variable name that is an opcode
+symbol
+    : opcode | variable | LOC | RELOC
+    ;
+
 expression
    : multiplyingExpression ((PLUS | MINUS) multiplyingExpression)*
    ;
@@ -76,6 +82,7 @@ multiplyingExpression
 atom
    : variable
    | LOC
+   | CHAR
    | RELOC
    | string
    | DECIMAL
@@ -251,22 +258,22 @@ DECIMAL
    : 'd' [0-9] +
    ;
 
-
 OCTAL
    : 'o' [0-7] +
    ;
 
-
 DECIMAL_MINUS
    : 'dm' [0-9] +
    ;
 
-
 STRING
    : '<' [a-zA-Z0-9$*,%/:?]*
    ;
 
-
+CHAR
+    : [a-zA-Z0-9>.] '>' 
+    ;
+      
 COMMENT
    : '"' ~ [\r\n]*
    ;
diff --git a/pdp7parse/src/test/resources/as.s b/pdp7parse/src/test/resources/as.s
new file mode 100644
index 0000000..9382fac
--- /dev/null
+++ b/pdp7parse/src/test/resources/as.s
@@ -0,0 +1,1025 @@
+"** 05-1-4.pdf page 32
+" as
+
+   jms init1			" initialize for pass 1
+
+assm1:
+   lac eofflg
+   sza				" saw EOF?
+   jmp assm2			"  no.
+   lac passno			" yes
+   sza				" pass==0?
+   jmp finis			"  no, pass 2: done
+   jms init2			" initialize for pass 2
+
+assm2:				" main loop
+   jms gchar			" get character
+   sad d4			" comma space or tab?
+   jmp assm1			"  yes, ignore
+   sad d5			" newline or ';'??
+   jmp assm1			"  yes, ignore
+   lac char
+   dac savchr			" no, push back
+   jms gpair
+   lac rator
+   jms betwen; d1; d6		" plus, minus, space comma tab or semi?
+   jmp assm3			"  no
+   jms expr
+   lac passno
+   sza				" pass 1?
+   jms process			"  no, process on pass 2
+   isz dot+1			" increment "."
+   nop
+   lac dot+1
+   and o17777
+   sad dot+1			" overflow?
+   jmp assm1			"  no
+   jms error; >>		" '>' error: past end of memory
+   dzm dot+1			" start again at zero!
+   jmp assm1
+
+assm3:
+   lac rand
+   sad d2
+   jmp assm4			"  yes
+   sza
+   jmp assm6
+   lac rator			" fetch operator
+   sza				" ":"?
+   jmp assm6			"  no
+   lac rand+1
+   jms betwen; dm1; d10		" numeric and 0..9?
+   jmp assm6			"  no
+   dac name			" yes, save as name
+   tad fbxp
+   dac lvrand
+   lac i lvrand			" get fbx entry
+   dac name+1			" save in second word of name
+   isz i lvrand			" increment fbx entry
+   lac o146			" get 'f'
+   dac name+2			" save in third word of name
+   dzm name+3			" clear fourth word
+   jms tlookup			" look it up
+   -1
+"** 05-1-4.pdf page 33
+   dac fbflg			" set fbflg to -1
+assm4:
+   lac rand+1
+   tad d4
+   dac lvrand
+   lac rator			" get operator
+   sza				" ':'?
+   jmp assm5			"  no
+   lac dot			" load dot type
+   dac r			" save as r type
+   lac dot+1			" get dot value
+   dac r+1			" save as r value
+   jmp 1f
+
+assm5:
+   jms gpair
+   jms expr
+1:
+   lac r
+   dac i lvrand
+   isz lvrand
+   lac r+1
+   dac i lvrand
+   lac fbflg
+   sna				" fb flag set?
+   jmp assm1			"  no
+   dzm fbflg			" clear fb flag
+   dzm name+1
+   lac o142			" get 'b'
+   dac name+2
+   jms lookup
+   jmp assm4
+
+assm6:
+   jms error; x>		" "x" error -- various errors
+   jmp assm1
+
+init1: 0			" init for pass 1
+   lac d1
+   sys write; 1f; 2f-1f		" output I, newline
+   dzm passno			" clear passno
+   lac o56040			" load ". "
+   dac dot-4
+   lac o56056			" load ".."
+   dac cmflx-4
+   lac o40040			" pad ". " and ".." names with spaces
+   dac dot-3
+   dac dot-2
+   dac dot-1
+   dac cmflx-3
+   dac cmflx-2
+   dac cmflx-1
+   dzm iof			" clear input fd
+   jms init
+   jmp i init1
+1:
+   0111012			" I\n
+2:
+
+init2: 0			" start pass 2
+   lac d1
+"** 05-1-4.pdf page 34
+   dac passno			" passno = 1
+   sys write; 1f; 2f-1f		" output II
+   jms init
+   lac o17
+   sys creat; 2f		" create a.out
+   dac bfo
+   sys open; 2f; 0		" open a.out for read too!
+   dac bfi
+   dzm bufadd
+   jms copyz; buf; 64		" clear buffer
+   jmp i init2
+1:
+   0111111;012000		" II\n
+2:
+   0141056;0157165;0164040;040040	" a.out
+
+init: 0				" common init for both passes
+   lac i 017777
+   dac narg			" save arg count
+   lac 017777
+   tad d1
+   dac fname			" point to first file name
+   -1
+   dac eofflg
+   jms ioinit
+   dzm savchr			" clear saved char
+   dzm comflg			" clear line comment flag
+   lac d1
+   dac dot			" set "." type to one??
+   dzm dot+1			" clear "." value??
+   dzm cmflx			" set ".." type to zero??
+   lac d4096			" set ".." value to 4K
+   dac cmflx+1
+   dzm fbflg			" clear f/b flag and array
+   jms copyz; fbxp: fbx; 10
+   jmp i init			" return
+
+finis:
+   lac iof			" close input file
+   sys close
+   jms bufwr			" flush output buffer
+   lac bfi			" close a.out input fd
+   sys close
+   lac bfo			" close a.out output fd
+   sys close
+   -1
+   tad namsiz
+   cma				" get positive count of namelist entries
+   rcl				" multiply by 6 to get words
+   dac char
+   rcl
+   tad char
+   dac 1f
+   lac o17			" ?? creat mode bits??
+   sys creat; n.out		" create "n.out"
+   dac bfi
+   sys write; namlst; 1: 0	" write name list
+   lac bfi
+   sys close			" close n.out
+   sys exit
+
+"** 05-1-4.pdf page 35
+n.out:
+   0156056;0157165;0164040;040040	" n.out
+
+process: 0
+   lac dot+1			" get "." value
+   dac lvrand
+   lac dot			" get "." type??
+   sad d3			" three (user defined symbol?)?
+   jmp proc4			"  yes, give "." error
+   sza				" zero?
+   jmp proc1			"  no
+   -1				" yes (".." type)
+   tad cmflx+1
+   cma
+   tad lvrand			" get "." - ".."
+   dac lvrand
+
+proc1:
+   lac lvrand
+   spa				" is relocated value positive?
+   jmp proc4			"  no, give "." error
+   and o17700			" mask to block
+   sad bufadd			" same block as buffer?
+   jmp proc2			"  yes, same block
+   jms bufwr			" different block, write out current block
+   jms copyz; buf; 64		" clear buffer
+   lac lvrand
+   and o17700
+   dac bufadd
+   dac 1f
+   lac bfi
+   sys seek; 1: 0; 0		" seek to current block from file
+   spa
+   jmp proc2
+   lac bfi
+   sys read; buf; 64
+
+proc2:
+   lac lvrand			" destination address
+   and o77			" word within block
+   jms betwen; dm1; maxsto	" inside buffer?
+   dac maxsto			"  no, increment buffer size
+   tad bufp			" add pointer to buffer
+   dac lvrand			" save buffer pointer
+   lac r			" get r type?
+   sna				" non-zero ("." or label)?
+   jmp proc3			"  no: zero (..)
+   sad d3			" three (user label)?
+   jmp proc5			"  yes
+   lac cmflx+1			" get ".." value
+   tad r+1			" add to r value
+   dac r+1
+
+proc3:
+   lac r+1			" get r value
+   dac i lvrand			" save in buffer
+   jmp i process		" return
+
+proc4:
+   jms error; .>
+   lac d1
+   dac dot		" set '.' type to 1
+"** 05-1-4.pdf page 36
+   dzm dot+1		" clear dot value
+   jmp skip
+
+proc5:
+   jms error; u>
+   jmp proc3
+
+bufwr: 0		" write current buffer to a.out file
+   lac bfo
+   sys seek; bufadd: 0; 0
+   isz maxsto
+   lac bfo
+   sys write; bufp: buf; maxsto: -1
+   -1
+   dac maxsto
+   jmp i bufwr
+
+number: 0		" print decimal number: append to buffer at index 8
+   dac 3f		" save number
+   lac d1000
+   dac 2f		" save divisor
+1:
+   lac 3f
+   cll
+   idiv; 2: 0
+   dac 3f
+   lacq
+   tad o60		" add ascii '0'
+   dac i 8		" save char
+   lac 2b
+   cll
+   idiv; 10
+   lacq
+   dac 2b
+   sza
+   jmp 1b
+   jmp i number
+3: 0
+
+	" get character from buffer (two characters per word)
+	" call with:
+	"   jms getsc; pointer_pointer
+	" where pointer_pointer refers to a pointer to buffer
+	" high bit in pointer indicates low char is next
+getsc: 0
+   lac i getsc			" get pointer pointer
+   dac sctalp			" save
+   isz getsc			" skip pointer pointer
+   lac i sctalp			" fetch pointer
+   dac sctal			" save
+   add o400000			" toggle high bit, increment on wrap
+   dac i sctalp			" save pointer back
+   ral				" rotate high bit into link reg
+   lac i sctal			" load word from buffer
+   szl				" skip if link zero
+   lrss 9			"  link set: get high char from word
+   and o177			" strip to 7 bits
+   jmp i getsc			" return
+
+	" save characters: word after call is addr of pointer, -count pair
+	" high bit in pointer used to indicate high/low
+putsc: 0
+   and o177			" strip character to 7 bits
+   lmq				" save in MQ
+   lac i putsc			" get address of pointer
+   dac sctalp			" save
+   isz putsc			" skip over pointer to pointer
+"** 05-1-4.pdf page 37
+   lac i sctalp			" get pointer
+   dac sctal			" save
+   add o400000			" toggle pointer sign bit, increment on wrap
+   dac i sctalp			" save pointer
+   sma cla			" skip if minus & clear AC
+   jmp 1f			"  AC positive
+   llss 27			" get char in high 9 bits, zero in low
+   dac i sctal			" store word
+   lrss 9			" shift char back down
+   jmp i putsc			" return
+
+1:
+   lac i sctal			" load target word
+   omq				" or in low char from MQ
+   dac i sctal			" save word back
+   lacq				" restore character
+   jmp i putsc			" return
+
+sctalp: 0
+sctal: 0
+
+	" test if between two values (low,high]
+	" call with value in AC
+	"    jms betwen; lowptr; highptr
+	" skip returns if AC in range
+	" AC returned unmodified
+	" NOTE!
+	" the test appears to be non-inclusive
+	" on the low side, and inclusive on the high side
+
+betwen: 0
+   dac 2f			" save value to test
+   lac i betwen			" load range start addr
+   dac 3f			" save
+   isz betwen			" increment return PC
+   lac i 3f			" load range start
+   cma				" complement
+   tad 2f			" AC = AC - start - 1
+   spa				" still positive?
+   jmp 1f			"  no
+   lac i betwen			" load range end addr
+   dac 3f			" save
+   isz betwen			" skip range high on return
+   lac i 3f			" load range high
+   cma
+   tad d1			" negate AC (~AC + 1)
+   tad 2f			" add test value
+   spa				" if not positive, don't skip on return!!
+1:
+   isz betwen			" discard "high" (or skip return)!
+   lac 2f			" restore AC
+   jmp i betwen			" return
+2: 0
+3: 0
+
+	" zero a block of memory
+	" call with:
+	"   jms copyz; ptr; count
+copyz: 0
+   -1
+   tad i copyz			" get address-1
+   dac 8			" store in first "index register"
+   isz copyz			" skip over address
+   lac i copyz			" load count
+   cma				" get -count
+   tad d1
+   dac 2f			" save
+   isz copyz			" skip over count
+1:
+   dzm i 8			" increment index, clear word
+   isz 2f			" increment count, skip if done
+   jmp 1b			"  not done, loop
+   jmp i copyz			" done: return
+"** 05-1-4.pdf page 38
+2: 0
+
+error: 0
+   lac passno			" get pass number
+   sza				" pass one?
+   jmp 1f			"  no, pass two
+   isz error			" pass one: skip error char
+   jmp i error			" return
+1:
+   -1
+   tad mesp			" get mes-1
+   dac 8			" save as index
+   lac i error			" get error
+   dac i 8			" save in mess
+   lac o40			" get space
+   dac i 8			" save in mess
+   lac rator			" get operator
+   sad d5			" word break (semi, newline)?
+   jmp 1f			"  yes
+   lac savchr			" no, get saved char
+   sad o12			" newline?
+   jmp 1f			"  yes
+   lac lineno			" get lineno
+   jmp 2f
+1:
+   -1
+   tad lineno			" get lineno -1
+2:
+   jms number			" convert line number to ascii
+   lac o12			" get newline
+   dac i 8			" append to mess
+   -2
+   tad mesp
+   cma
+   tad 8
+   dac 1f
+   lac d1
+   sys write; mesp: mes; 1: 0
+   isz error
+   jmp i error
+
+skip:
+   lac rator			" get operator
+   sad d5			" EOL?
+   jmp assm1			"  yes, start from top
+1:
+   jms gchar			" loop until ';' or NL seen
+   sad d5			" EOL?
+   jmp assm1			"  yes, start from top
+   jmp 1b
+
+ioinit: 0
+   jms copyz; iobuf; 64		" clear iobuf
+   lac iof
+   sys read; iobufp: iobuf; 64	" read from input
+   sna				" EOF?
+   jms nextfil			"  yes, skip to next file
+   lac iobufp			" load iobuf pointer
+   dac tal			" save
+   -129				" get -bytecount-1
+   dac talc			" save as count
+"** 05-1-4.pdf page 39
+   jmp i ioinit			" return
+
+nextfil: 0			" advance to next file
+   lac d1
+   dac lineno			" reset lineno to 1
+   lac iof			" load input fd
+   sza				" zero?
+   sys close			"  no: close
+nf1:
+   lac narg			" load arg count
+   sad d4			" ==4? (done)
+   skp				"  yes, skip
+   jmp 1f			"   no
+   dzm eofflg			" flag eof (set to zero)
+   jmp i nextfil		" return
+1:
+   tad dm4			" subtract 4
+   dac narg			" store narg
+   lac fname			" get fname pointer
+   tad d4			" subtract 4
+   dac fname			" save fname
+   sys open; fname: 0; 0	" open fname
+   dac iof			" save fd
+   sma				" open ok?
+   lac passno			"  yes, load pass number
+   sna				"   open failed: skip or open ok, pass 2
+   jmp nextfil i		"    pass 1, open OK, return.
+   lac fname			" load filename pointer
+   dac 1f			" save for write
+   lac d1			" stdout
+   sys write; 1; 0; 4		" output filename
+   lac iof			" load fd
+   sma				" open ok?
+   jmp 1f			"  yes, continue
+   lac d1
+   sys write; emes; 2		" output "? \n"
+   sys exit			" quit.
+1:
+   lac d1
+   sys write; emes+1; 1		" output newline after filename
+   jmp i nextfil		" return
+emes:
+   040077;012000		" question mark, space, newline
+
+gchar: 0
+   lac savchr			" load saved char
+   dzm savchr			" clear saved char
+   sza				" was there a saved char?
+   jmp gch3			"  yes, process it
+   lac eofflg			" no: get eof flag
+   sza				" seen eof (zero if true)
+   jmp 1f			"  no.
+   lac o12			" yes: get NL
+   jmp gch3			" process it
+1:
+   isz talc			" increment (negative count): is it zero?
+   skp				"  non-zero: skip
+   jms ioinit			"   count was zero: call ioinit
+   jms getsc; tal		" fetch character
+   sna				" is char non-zero?
+   jmp gchar+1			"  no: char is zero, get another
+"** 05-1-4.pdf page 40
+   sad o177			" is char 0177
+   jmp gchar+1			"  yes, ignore it
+   sad o12			" is char newline?
+   skp				"  yes
+   jmp 1f			"   no
+   dzm comflg			" saw newline: clear comflg
+   isz lineno			" increment line number
+1:
+   sad o42			" is char '"'?
+   dac comflg			"  yes, set comflg
+   dac char			" save char
+   lac comflg			" load comflg
+   sza				" comflg clear?
+   jmp gchar+1			"  no: ignore reset of line
+   lac char			" get char
+
+gch3:
+   dac char			" save char in char
+   jms betwen; d0; o200		" legal char?
+   cla				"  no, clear
+   tad lactab			" add to "lac labtab+1"
+   dac .+1			" save as next instruction
+   lac 0			" get character class in AC
+   jmp i gchar			" return
+
+gsymb: 0
+   jms gchar			" get char
+   dac rator			" save class
+   tad jmpsw1			" add table base instruction
+   dac 1f			" save for later
+   lac char			" what was it?
+   sad o74			" '<'??
+   jmp lqot			"  yes: process as "left quote"
+   dac namc			" no, save as namc
+   jms gchar			" get another
+   lac char			" what was it?
+   sad o76			" '>'?
+   jmp rqot			"  yes: process "right quote"
+   dac savchr			" no: save as savchr
+   lac namc			" restore first char
+   dac char			" resave as "char"
+1:
+   jmp 0			" jmpsw1[0] + class
+jmpsw1:				" indexed by character class
+   jmp .+1			" base instruction (added to class)
+   jmp i gsymb			" 0: ":" return
+   jmp i gsymb			" 1: "=" return
+   jmp i gsymb			" 2: "+" return
+   jmp i gsymb			" 3: "-" return
+   jmp gs1			" 4: comma, space, tab
+   jmp i gsymb			" 5: EOL (semi, newline)
+   jmp gs2			" 6: dot, star, letter
+   jmp gs3			" 7: digits
+
+badchr:				" here with bad char (class 8)
+   jms error; g>		" error "g"
+1:
+   jms gchar			" discard until newline
+   lac char
+   sad o12
+"** 05-1-4.pdf page 41
+   skp
+   jmp 1b
+   dac savchr			" push newline back
+   jmp gsymb+1			" restart gsymb
+
+lqot:				" left quote (<)
+   jms gchar			" get another char
+   lac o40
+   dac savchr			" put a space in savchr
+   lac char			" get quoted character
+   alss 9			" shift up 9 bits
+   jmp 1f			" join with right quote
+
+rqot:				" right quote (>)
+   lac namc			" get previous(?) char
+1:
+   dac rand+1			" save value
+   lac d7			" return as literal
+   dac rator
+   jmp i gsymb
+
+gs1:				" here with space, tab, comma
+   jms gchar			" get another char
+   sad d4			" another space?
+   jmp gs1			"  yes, loop
+   lac char			" no, save for later
+   dac savchr
+   jmp i gsymb			" return
+
+gs2:				" here with dot, star, letter
+   lac namep			" load name buffer pointer
+   dac tal1			" save in temp pointer
+   -7				" load negative char count
+   dac tal1c			" save as temp counter
+   lac char			" restore char
+   jms putsc; tal1		" save it in name buffer
+
+gnam1:				" here to collect a name
+   jms gchar
+   jms betwen; d5; d8		" alphanumeric?
+   jmp gnam3			"  no, done
+   lac char
+   jms putsc; tal1
+   isz tal1c
+   jmp gnam1
+
+gnam2:				" here when 8 characters read, eat the rest
+   jms gchar			" next char
+   jms betwen; d5; d8		" alphanumeric?
+   skp				"  no
+   jmp gnam2			"   yes, loop
+   lac char
+   dac savchr			" push last char back
+   jms lookup			" look up symbol
+   jmp i gsymb			" return
+
+gnam3:				" here before 8 characters
+   lac char			" push last char back
+   dac savchr
+1:
+   lac o40			" pad to 8 with spaces
+"** 05-1-4.pdf page 42
+   jms putsc; tal1
+   isz tal1c
+   jmp 1b
+   jms lookup
+   jmp i gsymb
+
+gs3:				" here with digit
+   dzm rand+1			" clear number
+   lac char
+   sad o60			" zero?
+   jmp 1f			"  yes
+   lac d10			" no: process as decimal
+   jmp 2f
+1:
+   lac d8			" leading zero: process as octal
+2:
+   dac num2			" save radix
+
+num1:
+   lac rand+1			" get number
+   cll				" clear link
+   mul				" mutiply by radix
+num2: 0				" (radix stored here)
+   lacq				" get multiply result
+   tad char			" add char
+   tad dm48			" subtract '0'
+   dac rand+1			" save
+   jms gchar			" get another
+   sad d7			" digit?
+   jmp num1			"  yes: process
+   lac char			" no: get it
+   dac savchr			" push back
+   lac rand+1			" get number
+   jms betwen; dm1; d10		" between 0..9?
+   jmp i gsymb			"  no, return
+   dac name
+   tad fbxp			" make index into "fbx" array
+   dac name+1			" ???save??? (crushed below)
+   lac i name+1			" fetch fbx array entry
+   dac name+1			" save fbx count in name
+   lac savchr			" get break character
+   sad o146			" was it 'f'?
+   jmp 1f			"  yes
+   sad o142			" 'b'?
+   skp				"  yes
+   jmp i gsymb			"   not f or b, return
+   dzm name+1			" 'b': clear loaded fbx entry????
+1:				" here with DIGITS[fb]
+   dac name+2			" save f/b in third word of name
+   dzm name+3			" clear last word of name
+   lac d6			" class 6: alpha, dot star
+   dac rator			" save as (ope)rator
+   jms lookup			" lookup (create) symbol entry????
+   dzm savchr			" clear saved char
+   jmp i gsymb
+
+	" symbol lookup/creation
+	" tlookup doesn't create new entries???
+tlookup: 0
+      jmp 1f
+lookup: 0
+      dzm tlookup		" NOT a tlookup call
+1:
+"** 05-1-4.pdf page 43
+   -1
+   tad namlstp
+   dac 8			" get namelist ptr in index reg
+   lac namsiz
+   dac namc			" negative namelist size in namc
+lu1:
+   lac i 8			" get first word of namelist entry
+   sad name			" match name?
+   jmp 1f			"  yes
+   lac d5			" no, skip next 5 words
+lu2:
+   tad 8
+   dac 8
+   isz namc			" at end of list?
+   jmp lu1			"  no, keep going
+      lac tlookup		" yes, reached end
+      sna			" was tlookup?
+      jmp 2f			"  no, was lookup
+      lac fnamep
+      dac rand+1		" set rand+1 (value?) to fakename
+      jmp i tlookup		" return
+2:
+   lac name			" make new entry
+   dac i 8			" save word one of name
+   lac 8
+   dac rand+1
+   lac name+1
+   dac i 8			" save word two
+   lac name+2
+   dac i 8			" save word three
+   lac name+3
+   dac i 8			" save word four
+   lac d3
+   dac i 8			" set type(?) to three
+   dzm i 8			" clear value??
+   -1				" decrement namsiz
+   tad namsiz
+   dac namsiz
+   jmp i lookup			" return
+1:				" here when first word matched
+   lac i 8
+   sad name+1			" check second word
+   jmp 1f			"  matched, keep going
+   lac d4			" no match: skip ahead four words
+   jmp lu2
+1:
+   lac i 8
+   sad name+2			" does third word match?
+   jmp 1f			"  yes, keep going
+   lac d3			" no, skip ahead three words
+   jmp lu2
+1:
+   lac i 8
+   sad name+3			" final word match?
+   jmp 1f			"  yes
+   lac d2			" no, skip two words
+   jmp lu2
+1:				" name matched
+   -3
+   tad 8			" get next word minus three
+   dac rand+1			" return as value
+"** 05-1-4.pdf page 44
+      lac tlookup
+      sza
+      jmp i tlookup
+   jmp i lookup
+namep: name
+
+gpair: 0
+   jms gsymb			" get a symbol
+   lac rator			" get operator
+   sad d4			" space tab or comma?
+   jmp gpair+1			"  yes, get another
+   jms betwen; dm1; d6		" plus, minus, comma, semi?
+   jmp gp1			"  no
+   dzm rand			" clear "rand"
+   dzm rand+1
+   jmp i gpair			" return
+gp1:
+   sad d7			" digit??
+   lac d4			"  yes: switch to space??
+   tad dm4			" subtract 4??
+   dac rand			" save as operand??
+   jms gsymb
+   lac rator
+   sad d4			" whitespace?
+   jmp gp2			"  yes
+   jms betwen; dm1; d6		" anything but digit?
+   skp				"  no, a digit
+   jmp i gpair			"   yes, return
+   jms error; x>		" here with digit: give 'x' error
+   jmp skip
+gp2:				" here after whitespace
+   jms gchar			" get next char
+   jms betwen; d5; d8		" alphanumeric?
+   jmp gp3			"  no
+   lac char			" yes, push back
+   dac savchr
+   jmp i gpair
+gp3:
+   lac char			" push back break char
+   dac savchr
+   jms gsymb
+   jmp i gpair
+
+expr: 0
+   jms grand
+   -1
+   dac srand
+exp5:
+   lac rand
+   dac r
+   lac rand+1
+   dac r+1
+exp1:
+   lac rator
+   jms betwen; d1; d5		" plus, minus, comma, space, tab or comma?
+   jmp exp3			"  no
+   dac orator
+   jms gpair
+   jms grand
+   lac orator			" get operator back
+   sad d4			" comma space or tab?
+"** 05-1-4.pdf page 45
+   jmp exp2			"  no
+   jms oper; rand
+   jmp exp1
+exp2:
+   jms pickup
+   lac r
+   dac srand
+   lac r+1
+   dac srand+1
+   jmp exp5
+exp3:
+   sad d5
+   jmp exp4
+   jms error; x>
+   jmp skip
+exp4:
+   jms pickup
+   jmp i expr
+
+pickup: 0
+   lac srand
+   spa
+   jmp i pickup
+   lac d4
+   jms oper; srand
+   jmp i pickup
+
+grand: 0
+   lac rand
+   sad d2
+   skp
+   jmp i grand
+   lac rand+1
+   tad d4
+   dac rand+1
+   lac i rand+1
+   dac rand
+   isz rand+1
+   lac i rand+1
+   dac rand+1
+   jmp i grand
+
+	" called with
+	"    jms oper; argument
+oper: 0
+   tad opsw
+   dac oper1
+   -1
+   tad i oper		" pick up argument
+   dac 8		" store as index
+   isz oper		" skip argument
+   lac r
+   sad d3
+   jmp oper2
+   lac i 8
+   sad d3
+   jmp oper2
+oper1:
+   jmp 0
+opsw:
+   jmp .-1
+   jmp oplus
+   jmp ominus
+"** 05-1-4.pdf page 46
+   tad r
+   dac r
+   lac r+1
+   lmq
+   lac i 8
+   omq
+   jmp oret
+oplus:
+   tad r
+   dac r
+   lac r+1
+   tad i 8
+   jmp oret
+ominus:
+   cma
+   tad d1
+   tad r
+   dac r
+   -1
+   tad i 8
+   cma
+   tad r+1
+oret:
+   dac r+1
+   lac r
+   jms betwen; dm1; d2
+   skp
+   jmp i oper
+   jms error; r>
+   lac d1
+   dac r
+   jmp i oper
+oper2:
+   dac r
+   dzm r+1
+   jmp i oper
+
+d0: 0
+d1: 1
+d4096: 4096
+d2: 2
+d3: 3
+d4: 4
+d5: 5
+d6: 6
+d7: 7
+d8: 8
+o12: d10: 10
+dm1: -1
+o40: 040
+o60: 060
+dm48: -48
+o400000: 0400000
+o177: 0177
+dm4: -4
+o200: 0200
+o42: 042
+o142: 0142
+o40040: 040040		" space, space
+o56056: 056056		" ".."
+o56040: 056040		" ". "
+"** 05-1-4.pdf page 47
+o146: 0146
+o17777: 017777
+d1000: 1000
+o17: 017
+o17700: 017700
+o77: 077
+o74: 074
+o76: 076
+
+namsiz: -2		" negative numberof namelist entries
+namlstp: namlst		" pointer to namelist
+fnamep: fakename	" pointer to fake namelist entry
+lactab: lac .+1		" character (operator) class table (8 unless noted)
+8;8;8;8;8;8;8;8
+8;4;5;8;8;8;8;8		" TAB=4 NL=5
+8;8;8;8;8;8;8;8
+8;8;8;8;8;8;8;8
+4;8;8;8;8;8;8;8		" SP=4
+8;8;6;2;4;3;6;8		" *=6 +=2 ,=4 -=3 .=6
+7;7;7;7;7;7;7;7		" digits=7
+7;7;0;5;8;1;8;8		" :=0 ;=5 ==1
+8;6;6;6;6;6;6;6		" A-Z=6
+6;6;6;6;6;6;6;6
+6;6;6;6;6;6;6;6
+6;6;6;8;8;8;8;8
+8;6;6;6;6;6;6;6		" a-z=6
+6;6;6;6;6;6;6;6
+6;6;6;6;6;6;6;6
+6;6;6;8;8;8;8;8
+
+fbflg: .=.+1		" f/b label flag
+tal: .=.+1		" iobuf pointer
+talc: .=.+1		" -bytecount-1
+tal1: .=.+1		" namebuf pointer
+tal1c: .=.+1		" -bytecount-1
+narg: .=.+1		" argc
+lvrand: .=.+1		" numeric constant, word address
+eofflg: .=.+1		" 0 on EOF??
+namc: .=.+1		" saved char, temporary
+passno: .=.+1		" 0=pass1, 1=pass2
+char: .=.+1		" current character
+savchr: .=.+1		" pushed back char
+comflg: .=.+1		" comment flag
+rator: .=.+1		" (opo)rator (char type)
+orator: .=.+1		" ?? (op)orator
+rand: .=.+2		" ?? (ope)rand (type/address pair)
+srand: .=.+2		" ?? another operand
+r: .=.+2		" ?? yet another??
+name: .=.+4		" buffer for accumulating names
+buf: .=.+64		" a.out output buffer
+iobuf: .=.+64		" input buffer
+fbx: .=.+10		" forward/backward counters
+mes: .=.+20		" (error) message buffer
+iof: .=.+1		" source file fd
+bfi: .=.+1		" a.out input fd
+bfo: .=.+1		" a.out output fd
+lineno: .=.+1		" source file line number
+
+fakename: .=.+6		" dummy namelist entry returned by tlookup??
+namlst:			" symbol table
+.=.+4			" dot name
+dot:			" dot type, value
+.=.+6			" dot dot name
+cmflx:			" dotdot type, value
+		" namelist (symbol table) entries are 6 words.
+		" four words of symbol (space padded) name
+		" next word is type??
+		"   0: initial dotdot type
+		"   1: initial dot type (reset on error)
+		"   3: set by "lookup" (user symbol)
+		" last word is value??
diff --git a/pdp7parse/src/test/resources/bc.s b/pdp7parse/src/test/resources/bc.s
new file mode 100644
index 0000000..b857335
--- /dev/null
+++ b/pdp7parse/src/test/resources/bc.s
@@ -0,0 +1,288 @@
+" bc
+
+   jmp start
+rinit:
+   jms initio
+   jmp .+1 i
+initio: 0
+   lac inter-1
+   dac fetch
+   jmp rinit
+   jms inter
+inter: 0
+   las
+   and o17
+   sza
+   jms trace
+   lac pc i
+   dac instr
+   lac pc
+   and o10000
+   sna
+   jmp badpc
+   lac sp
+   and o17700
+   sad o17700
+   jmp badsp
+   and o10000
+   sna
+   jmp badsp
+   lac instr
+   sad insasg
+   skp
+   jmp inter i
+   -4
+   tad sp
+   dac t1
+   lac t1 i
+   and o10000
+   sna
+   jmp badasgn
+   lac instr
+   jmp inter i
+
+trace: 0
+   and d1
+   sza
+   jms dtrace
+   las
+   and d2
+   sza
+   jms ddisp
+   las
+   and d4
+   sza
+   jms histog
+   las
+   and d8
+   sza
+   jmp stop
+   jmp trace i
+
+dtrace: 0
+   lac pc
+   dac 8
+   lac 8 i
+   dac instr
+   lac 8
+   jms octal; -4
+   law 040
+   jms putc
+   lac instr
+   cll; lrs 14
+   tad lacop
+   dac .+1
+   lac ..
+   jms putc
+   law 040
+   jms putc
+   lac instr
+   jms octal; -4
+   
+   lac instr
+   sad inslitr
+   skp
+   jmp 1f
+   law 040
+   jms putc
+   lac 8 i
+   jms octal; -6
+1:
+   law 012
+   jms putc
+   jms flush
+   jmp dtrace i
+
+ddisp: 0
+   jms dspinit
+   lac dspbp
+   dac 8
+   lac dp
+   sad olddp
+   skp
+   jms dspblk
+   lac pc
+   jms dspnt
+   lac sp
+   jms dspnt
+   lac lastv
+   jms dspnt
+   -1
+   dac B i
+   lac pbs i
+   sza
+   jmp .-2
+   jmp ddisp i
+
+dspblk: 0
+   lac dspbuf
+   dac 8
+   lac dp
+   dac t1
+   dzm t2
+1:
+   lac t1
+   sna
+   jmp 1f
+   lac o216000 " dx -20
+   dac 8 i
+   lac t2
+   tad o20
+   dac t2
+   lac t1
+   tad d1
+   dac t3
+   lac t3 i
+   jms dspnt
+   lac t1 i
+   dac t1
+   jmp 1b
+1:
+   lac o160020 " sx 20
+   tad t2
+   dac dspbuf i
+   dac 8 i
+   lac 8
+   dac dspbp
+   jmp dspblk i
+
+dspnt: 0
+   and o7777
+   lrss 2
+   xor o164000 " sy 0
+   dac 8 i
+   lac o17010
+   dac 8 i
+   jmp dspnt i
+
+dspinit: 0
+   -1
+   tad dspinit
+   dac dspinit
+   -300
+   tad lastv
+   dac lastv
+   dac dspbuf
+   -1
+   dac dspinit i
+   dac dspbuf i
+   dzm olddp
+   lac dspbuf
+   sys capt
+   law 13
+   sys sysloc
+   dac pbs
+   jmp dspinit i
+
+histog: 0
+   jms hisinit
+   lac pc
+   lrs 6
+   and o77
+   tad histbuf
+   dac t1
+   isz t1 i
+   jmp histog i
+   jmp .
+
+hisinit: 0
+   -1
+   tad hisinit
+   dac hisinit
+   -1
+   dac hisinit i
+   -64
+   dac t1
+   tad lastv
+   dac lastv
+   dac histbuf
+   tad dm1
+   dac 8
+1:
+   dsm 8 i
+   isz t1
+   jmp 1b
+   jmp hisinit i
+
+histbuf: 0
+olddp: 0
+dspbuf: 0
+dspbp: 0
+instr: 0
+obs: 0
+inslitr: n 5
+insasg: b 1
+o17: 017
+d8: 8
+o77: 077
+o10000: 010000
+d5: 5
+o60: 060
+o7777: 07777
+o216000: 0216000
+o160020: 0160020
+o20: 020
+o164000: 0164000
+o17010: 017010
+o17700: 017700
+d2: 2
+
+lacop: lac .
+   a>;b>;c>;f>;n>;s>;t>;u>;x>;y>
+
+badpc:
+   jms flush
+   lac d1
+   sys write; mpc; mpcs
+   jmp stop
+badsp:
+   jms flush
+   lac d1
+   sys write; msp; msps
+   jmp stop
+badasgn:
+   jms flush
+   lac d1
+   sys write; mas; mass
+   jmp stop
+mpc:
+   012;<pc>;012
+mpcs = .-mpc
+msp:
+   012;<sp>;012
+msps = .-msp
+mas:
+   012;<as>;012
+mass = .-mas
+
+octal: 0
+   lmq
+   lac d5
+   tad octal i
+   cma
+   dac 2f
+   sna
+   jmp 3f
+1:
+   llss 3
+   isz 2f
+   jmp 1b
+3:
+   lac octal i
+   dac 2f
+   lacq
+   dac 2f+1
+1:
+   lac 2f+1
+   lmq
+   ecla llss 3
+   tad o60
+   jms putc
+   lac 2f+1
+   alss 3
+   dac 2f+1
+   isz 2f
+   jmp 1b
+   isz octal
+   jmp octal i
+2: 0;0
diff --git a/pdp7parse/src/test/resources/bi.s b/pdp7parse/src/test/resources/bi.s
new file mode 100644
index 0000000..f8abd9d
--- /dev/null
+++ b/pdp7parse/src/test/resources/bi.s
@@ -0,0 +1,433 @@
+" bi
+
+start:
+   jms initio
+   -1
+   tad .main
+   dac pc
+
+fetch:
+   lac pc i
+   lmq
+   and o17777
+   dac addr
+   ecla lls 4
+   tad .+3
+   dac .+1
+   jmp .. i
+   jmp . i
+   autop; binop; consop; ifop; etcop; setop; traop
+   unaop; extop; aryop
+
+
+ifop:
+   -2
+   tad sp
+   dac sp
+   lac sp i
+   dac t1
+   lac t1 i
+   sza
+   jmp fetch
+   -1
+   tad addr i
+   dac pc
+   jmp fetch
+
+autop:
+   lac addr
+   tad dp
+   dac sp i
+   isz sp
+   isz sp
+   jmp fetch
+
+binop:
+   -2
+   tad sp
+   dac sp
+   tad dm1
+   dac t4
+   tad dm1
+   dac t3
+   lac t3 i
+   dac t1
+   lac sp i
+   dac t2
+   lac t4
+   dac t3 i
+   lac addr
+   tad .+3
+   dac .+1
+   jmp .. i
+   jmp . i
+   basg; bor; band; beq; bne; ble; blt; bge; bgt; brsh; blsh
+   badd; bmin; bmod; bmul; bdiv
+
+basg:
+   lac t2 i
+   dac t1 i
+   dac t4 i
+   jmp fetch
+
+bor:
+   lac t1 i
+   lmq
+   lac t2 i
+   omq
+   dac t4 i
+   jmp fetch
+
+band:
+   lac t1 i
+   and t2 i
+   dac t4 i
+   jmp fetch
+
+beq:
+   lac t1 i
+   xor t2 i
+   sna cla
+   lac d1
+   dac t4 i
+   jmp fetch
+
+bne:
+   lac t1 i
+   xor t2 i
+   sza
+   lac d1
+   dac t4 i
+   jmp fetch
+
+ble:
+   lac t2 i
+   cma
+   tad t1 i
+   spa cla
+   lac d1
+   dac t4 i
+   jmp fetch
+
+blt:
+   lac t1 i
+   cma
+   tad t2 i
+   sma cla
+   lac d1
+   dac t4 i
+   jmp fetch
+
+bge:
+   lac t1 i
+   cma
+   tad t2 i
+   spa cla
+   lac d1
+   dac t4 i
+   jmp fetch
+
+bgt:
+   lac t2 i
+   cma
+   tad t1 i
+   sma cla
+   lac d1
+   dac t4 i
+   jmp fetch
+
+brsh:
+blsh:
+   hlt
+
+badd:
+   lac t1 i
+   tad t2 i
+   dac t4 i
+   jmp fetch
+
+bmin:
+   lac t1 i
+   cma
+   tad t2 i
+   cma
+   dac t4 i
+   jmp fetch
+
+bmod:
+   lac t2 i
+   dac .+4
+   lac t1 i
+   cll; idiv; ..
+   dac t4 i
+   jmp fetch
+
+bmul:
+   lac t2 i
+   dac .+4
+   lac t1 i
+   cll; mul; ..
+   lacq
+   dac t4 i
+   jmp fetch
+
+bdiv:
+   lac t2 i
+   dac .+4
+   lac t1 i
+   cll; idiv; ..
+   lacq
+   dac t4 i
+   jmp fetch
+
+consop:
+   lac sp
+   tad d1
+   dac sp i
+   isz sp
+   lac addr
+   dac sp i
+   isz sp
+   jmp fetch
+
+etcop:
+   lac addr
+   tad .+3
+   dac .+1
+   jmp .. i
+   jmp . i
+   mcall; mark; call; vector; litrl; goto; retrn; escp
+
+mcall:
+   -2
+   tad sp
+   dac t1
+   lac t1 i
+   dac t2
+   -1
+   tad t2 i
+   lmq
+   lac dp
+   dac t1 i
+   lac t1
+   dac dp
+   isz t1
+   lac pc
+   dac t1 i
+   lacq
+   dac pc
+   jmp fetch
+
+mark:
+   -1
+   tad sp
+   dac t2
+   tad dm1
+   dac t1
+   lac t1 i
+   dac t3
+   lac t3 i
+   dac t2 i
+   lac ap
+   dac t1 i
+   lac t1
+   dac ap
+   jmp fetch
+
+call:
+   lac ap
+   tad d1
+   dac 8
+   dac 9
+1:
+   lac 8 i
+   dac t1
+   lac t1 i
+   dac 9 i
+   isz 8
+   -1
+   tad sp
+   sad 8
+   skp
+   jmp 1b
+   lac ap i
+   lmq
+   lac dp
+   dac ap i
+   lac ap
+   dac dp
+   isz ap
+   -1
+   tad ap i
+   dac t1
+   lac pc
+   dac ap i
+   lacq
+   dac ap
+   lac t1
+   dac pc
+   jmp fetch
+
+vector:
+   -2
+   tad sp
+   dac sp
+   tad dm2
+   dac t1
+   lac sp i
+   dac t2
+   lac t1 i
+   dac t3
+   lac t3 i
+   tad t2 i
+   dac t1 i
+   jmp fetch
+
+litrl:
+   lac sp
+   tad d1
+   dac sp i
+   isz sp
+   lac pc i
+   dac sp i
+   isz sp
+   jmp fetch
+
+goto:
+   -2
+   tad sp
+   dac sp
+   lac sp i
+   dac t1
+   -1
+   tad t1 i
+   dac pc
+   jmp fetch
+   
+retrn:
+   -2
+   tad sp
+   dac sp
+   lac sp i
+   dac t1
+   lac t1 i
+   lmq
+   lac dp
+   dac sp
+   dac t1
+   lac sp i
+   sna
+   jmp stop
+   dac dp
+   isz sp
+   lac sp
+   dac t1 i
+   lac sp i
+   dac pc
+   lacq
+   dac sp i
+   isz sp
+   jmp fetch
+
+escp:
+   law 2
+   tad pc
+   dac t1
+   jmp t1 i
+
+setop:
+   lac addr
+   tad dp
+   dac sp
+   jmp fetch
+
+traop:
+   -1
+   tad addr
+   dac pc
+   jmp fetch
+
+unaop:
+   -1
+   tad sp
+   dac t3
+   tad dm1
+   dac t2
+   lac t2 i
+   dac t1
+   lac t3
+   dac t2 i
+   lac addr
+   tad .+3
+   dac .+1
+   jmp .. i
+   jmp . i
+   uadr; umin; uind; unot
+
+uadr:
+   lac t1
+   dac t3 i
+   jmp fetch
+
+umin:
+   -1
+   tad t1 i
+   cma
+   dac t3 i
+   jmp fetch
+
+uind:
+   lac t1 i
+   dac t2 i
+   jmp fetch
+
+unot:
+   lac t1 i
+   sna cla
+   lac d1
+   dac t3 i
+   jmp fetch
+
+extop:
+   lac addr
+   dac sp i
+   isz sp
+   isz sp
+   jmp fetch
+
+aryop:
+   lac addr
+   tad dp
+   dac t1
+   tad d1
+   dac t1 i
+   jmp fetch
+
+a = 040000
+b = a+a
+c = b+a
+f = c+a
+n = f+a
+s = n+a
+t = s+a
+u = t+a
+x = u+a
+y = x+a
+
+d1: 1
+dm1: -1
+dm2: -2
+o17777: 017777
+
+t1: 0
+t2: 0
+t3: 0
+t4: 0
+addr: 0
+
+pc = 017
+
+sp: stack
+dp: stack
+ap: stack
+stack: 0
\ No newline at end of file
diff --git a/pdp7parse/src/test/resources/s1.s b/pdp7parse/src/test/resources/s1.s
index 8dcf364..f50088c 100644
--- a/pdp7parse/src/test/resources/s1.s
+++ b/pdp7parse/src/test/resources/s1.s
@@ -3,22 +3,22 @@
 .. = 0
 t = 0
 orig:
-   hlt
-   jmp pibreak
+   hlt				" overwritten with interrupt return addr
+   jmp pibreak			" dispatch to interrupt processing
 
 . = orig+7
-   -1
+   -1				" only ever set (to -1): never read?!
 
-. = orig+020
-   1f
-   iof
-   dac u.ac
-   lac 020
-   dac 1f
+. = orig+020			" syscall (CAL) processing
+   1f				" addr for "CAL I": store return here on "CAL"
+   iof				" interrupts off
+   dac u.ac			" save user AC
+   lac 020			" save user return addr
+   dac 1f			" save as if "CAL I"
    lac 1f-1
-   dac 020
-   lac u.ac
-   jmp 1f+1
+   dac 020			" restore location 20
+   lac u.ac			" restore user AC
+   jmp 1f+1			" join "CAL I" processing
    1f
 1: 0
    iof				" interrupts off
@@ -49,7 +49,7 @@ orig:
    jmp .. i			" dispatch system call
 
 . = orig+0100
-   jmp coldentry
+   jmp coldentry		" here to start kernel
    jms halt
 
 okexit:
@@ -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
@@ -77,6 +77,7 @@ sysexit:			" common system call exit code
    lac u.ac			" restore AC register
    jmp u.rq+8 i			" return to user
 
+	" scheduler / idle loop
 swap: 0
    ion
 1:
@@ -84,49 +85,49 @@ swap: 0
       jmp 1f
    jms lookfor; 1 " in/ready
       skp
-   jmp 1b
-   dzm maxquant
+   jmp 1b			" loop until a process becomes ready
+   dzm maxquant			" here with in/ready (self?)
    jmp 3f
-1:
-   dac 9f+t
-   jms lookfor; 2 " in/notready
+1:				" here with out/ready process
+   dac 9f+t			" save process pointer (swapped out) in t0
+   jms lookfor; 2 " in/notready	" find a swapped in process to swap out?
       jmp 1f
    jms lookfor; 1 " in/ready
       jmp 1f
    jmp 2f
 1:
    lac swap
-   dac u.swapret
+   dac u.swapret		" return to scheduler when swapped back
    iof
-   lac o200000
+   lac o200000			" change status to swapped out
    tad u.ulistp i
    dac u.ulistp i
    ion
-   jms dskswap; 07000
+   jms dskswap; 07000		" swap process out
    lac u.dspbuf
    sna
    jmp 2f
    law dspbuf
    jms movdsp
 2:
-   iof
-   lac o600000
+   iof				" disable interrupts
+   lac o600000			" change status (1->7?)
    tad 9f+t i
    dac 9f+t i
-   ion
-   jms dskswap; 06000
-   lac u.swapret
-   dac swap
-   lac o20
+   ion				" enable interrupts
+   jms dskswap; 06000		" read process in?
+   lac u.swapret		" set our return addr
+   dac swap			" to saved return addr
+   lac o20			" reset maxquant to 16 ticks
    dac maxquant
    lac u.dspbuf
-   sza
+   sza				" using display?
 "** 01-s1.pdf page 4
-   jms movdsp
+   jms movdsp			"  yes.
 3:
-   dzm uquant
+   dzm uquant			" no. reset process tick count
    iof
-   jmp swap i
+   jmp swap i			" return
 t = t+1
 
 swp:			" system call dispatch table
@@ -138,12 +139,18 @@ swp:			" system call dispatch table
 swn:
    .-swp-1 i		" count of system calls, plus indirect!
 
+	" AC/ new value for intflg (non-zero to ignore interrupt char)
+	"   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
@@ -154,7 +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
@@ -162,34 +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
 
diff --git a/pdp7parse/src/test/resources/s2.s b/pdp7parse/src/test/resources/s2.s
index 3424c44..4006ed5 100644
--- a/pdp7parse/src/test/resources/s2.s
+++ b/pdp7parse/src/test/resources/s2.s
@@ -110,7 +110,7 @@
       skp
    jms error
    lac d1
-   dac mode
+   dac mode			" save mode bits for access
    jms access
    jms dslot
    lac u.base
@@ -131,8 +131,8 @@
 .unlink:
    jms argname
    dac u.base
-   lac d1
-   dac mode
+   lac d1			" mode bit 1 (write?)
+   dac mode			" save for access call
    jms access
    dac d.i
    jms dput
@@ -162,8 +162,8 @@
    lac u.cdir
    jms namei; 0:0
       jms error
-   lac d1
-   dac mode
+   lac d1				" mode bit 1 (write?)
+   dac mode				" save for access call
    jms access
    jms copy; 1:0; d.name; 4
    jmp okexit
@@ -190,36 +190,39 @@
 "** 01-s1.pdf page 10
    jmp okexit
 
+	" open system call
+	"   sys open; filename_ptr; flags (0 for read, 1 for write)
+	" returns w/ "fd" in AC (or -1 if not found)
 .open:
-   jms arg
-   dac 0f
-   jms arg
-   sza
-   lac d1
-   sna
-   lac d2
-   dac mode
-   lac u.cdir
-   jms namei; 0:0
-      jms error
-   jms iget
-   jms access
-   lac i.flags
-   and o20
-   sna
-   jmp open1
-   lac mode
-   and d1
-   sna
-   jmp open1
-   lac u.uid
-   sma
-   jms error
-   jmp open1
+   jms arg			" get filename
+   dac 0f			" save for namei
+   jms arg			" get flags
+   sza				" zero (read)
+   lac d1			"  no: get write mode bit
+   sna				" non-zero (write)?
+   lac d2			"  no: get read mode bot
+   dac mode			" save for access call
+   lac u.cdir			" get current working directory
+   jms namei; 0:0		" search for file
+      jms error			" error: return -1
+   jms iget			" load inode
+   jms access			" check access (may return w/ error to user)
+   lac i.flags			" get file flags
+   and o20			" get directory bit
+   sna				" is directory?
+   jmp open1			"  no, join common code
+   lac mode			" get access mode
+   and d1			" get write bit
+   sna				" write access?
+   jmp open1			"  no, continue
+   lac u.uid			" yes: get uid?
+   sma				" negative? (-1 is superuser)
+   jms error			"  no: return error
+   jmp open1			" yes: join common code
 
 .creat:
-   lac d1
-   dac mode
+   lac d1			" mode bit 1 (write)
+   dac mode			" save for access call
    jms arg
    dac .+2
    jms copy; ..; name; 4
@@ -241,12 +244,12 @@
    jmp open1
 1:
    jms access
-   lac u.ac
-   and o17
+   lac u.ac			" get access bits from user AC (zero for lock!)
+   and o17			" mask to permissions
    jms icreat
-open1:
-   jms fassign
-      jms error
+open1:				" common exit for open/creat
+   jms fassign			" assign fd slot
+      jms error			"  none free, return -1
    jmp sysexit
 
 "** 01-s1.pdf page 11
@@ -275,63 +278,67 @@ open1:
    and d1
    sza
    jms error
-   lac i.flags
-   and o40
-   sna
-   jmp 1f
-   iof
-   lac ii
-   tad swr
+   lac i.flags			" get inode flags
+   and o40			" get special file bit
+   sna				" special?
+   jmp 1f			"  no
+   iof				" yes: disable interrupts
+   lac ii			" get i number
+   tad swr			" get read routine table addr
    dac .+1
-   jmp .. i
+   jmp .. i			" dispatch to read routine
 1:
-   lac u.base
-   dac 1f+1
-   lac u.count
-   dac 1f+2
-   lac f.badd
+   lac u.base			" get user base
+   dac 1f+1			" save as iread base
+   lac u.count			" get user count
+   dac 1f+2			" save as iread count
+   lac f.badd			" get file offset
 1:
    jms iread; ..; ..
    jmp exitrw
 
+	" write system call:
+	" AC/ fd
+	"   sys write; buffer; count
+	" AC/ count or -1 on error
 .write:
-   jms arg
-   and o17777
-   dac u.base
-   jms arg
-   dac u.count
-   tad u.base
-   jms betwen; u.base; o17777
-      jms error
-   dac u.limit
-   jms finac
-   lac f.flags
-   and d1
-   sna
-   jms error
-   lac i.flags
-   and o40
+   jms arg			" pick up buffer
+   and o17777			" mask to addr
+   dac u.base			" save as I/O base
+   jms arg			" pick up count
+   dac u.count			" save as count
+   tad u.base			" add base (get limit)
+   jms betwen; u.base; o17777	" check between base and end of memory
+      jms error			"  no: error
+   dac u.limit			" yes: save as limit
+   jms finac			" get fnode with fd from user AC
+   lac f.flags			" get open file table flags
+   and d1			" open for write?
+   sna				"  yes, skip
+   jms error			"   no: error
+   lac i.flags			" get inode flags
+   and o40			" get special bit?
 "** 01-s1.pdf page 12
-   sna
-   jmp 1f
-   iof
-   lac ii
-   tad sww
+   sna				" special?
+   jmp 1f			"  no
+   iof				" special file (device node)
+   lac ii			" get i number
+   tad sww			" get write routine
    dac .+1
-   jmp .. i
+   jmp .. i			" dispatch to write routine
+1:				" here with regular file
+   lac u.base			" get base
+   dac 1f+1			" save as iwrite arg 1
+   lac u.count			" get count
+   dac 1f+2			" save as iwrite 2
+   lac f.badd			" get fd offset
 1:
-   lac u.base
-   dac 1f+1
-   lac u.count
-   dac 1f+2
-   lac f.badd
-1:
-   jms iwrite; ..; ..
+   jms iwrite; ..; ..		" write to file
 
-exitrw:
-   dac u.ac
+exitrw:				" common exit for read/write system calls
+   dac u.ac			" save return in user AC
    tad f.badd
-   dac f.badd
-   jms iput
-   jms fput
-   jmp sysexit
+   dac f.badd			" update file offset
+   jms iput			" release inode
+   jms fput			" release fnode
+   jmp sysexit			" return to user
diff --git a/pdp7parse/src/test/resources/s3.s b/pdp7parse/src/test/resources/s3.s
index c0ca18d..2947c11 100644
--- a/pdp7parse/src/test/resources/s3.s
+++ b/pdp7parse/src/test/resources/s3.s
@@ -1,15 +1,21 @@
 "** 01-s1.pdf page 14
 " s3
 
+	" search for user (process)
+	" call:
+	"   jms searchu; worker_routine_addr
+	" worker called with copy of a process table entry in "lu"
+	"	can return directly (from caller of searchu)
+	"	index location 8 points to next process table entry
 searchu: 0
-   lac searchu i
-   dac 9f+t+1
-   -mnproc
-   dac 9f+t
-   law ulist-1
-   dac 8
+   lac searchu i		" fetch argument
+   dac 9f+t+1			" in t1
+   -mnproc			" loop counter
+   dac 9f+t			" in t0
+   law ulist-1			" ulist ptr
+   dac 8			" in index 8
 1:
-   lac 8 i
+   lac 8 i			" copy ulist entry to lu
    dac lu
    lac 8 i
    dac lu+1
@@ -17,86 +23,96 @@ searchu: 0
    dac lu+2
    lac 8 i
    dac lu+3
-   jms 9f+t+1 i
-   isz 9f+t
-   jmp 1b
-   isz searchu
+   jms 9f+t+1 i			" call argument as subroutine
+   isz 9f+t			" returned: loop done?
+   jmp 1b			"  no, do it again
+   isz searchu			" skip argument
    jmp searchu i
 t = t+2
 
+	" look for a process with matching status
+	"   jms lookfor; status
+	"    found: ulist ptr in AC
+	"   not found
 lookfor: 0
    jms searchu; 1f
-   isz lookfor
-   isz lookfor
+   isz lookfor			" skip argument
+   isz lookfor			" give skip return
    jmp lookfor i
-1: 0
+1: 0				" worker called by searchu
    lac lu
-   rtl; rtl; and o7
-   sad lookfor i
-   skp
-   jmp 1b i
+   rtl; rtl; and o7		" bits 0:2 of lu
+   sad lookfor i		" match argument?
+   skp				"  yes
+   jmp 1b i			"   no, return, keep going
    -3
-   tad 8
+   tad 8			" roll index 8 back to this entry
    and o17777
-   isz lookfor
-   jmp lookfor i
+   isz lookfor			" skip lookfor argument
+   jmp lookfor i		" non-skip return
 
+	" fork system call:
+	"   sys fork
+	"    return at +1 in parent, child pid in AC
+	"   return at +2 in child, parent pid in AC
 .fork:
-   jms lookfor; 0 " not-used
+   jms lookfor; 0 " not-used	" find an unused process slot
       skp
-      jms error
-   dac 9f+t
-   isz uniqpid
+      jms error			" none found- return error
+   dac 9f+t			" save ulist ptr in t0
+   isz uniqpid			" generate new pid
    lac uniqpid
-   dac u.ac
+   dac u.ac			" return in child pid in AC
    law sysexit
-   dac u.swapret
-   lac o200000
+   dac u.swapret		" return from system call when swapped back in
+   lac o200000			" change process status to out/ready (1->3)
    tad u.ulistp i
    dac u.ulistp i
-   jms dskswap; 07000
-   lac 9f+t
-   dac u.ulistp
-   lac o100000
+   jms dskswap; 07000		" swap parent out
+   lac 9f+t			" get unused ulist slot back
+   dac u.ulistp			" set ulist pointer
+   lac o100000			" mark child in/notready? (3->2)
    xor u.ulistp i
    dac u.ulistp i
-   lac u.pid
+   lac u.pid			" get old (parent) pid
 "** 01-s1.pdf page 15
-   dac u.ac
+   dac u.ac			" return parent pid in AC
    lac uniqpid
-   dac u.pid
-   isz 9f+t
-   dac 9f+t i
-   isz u.rq+8
-   dzm u.intflg
-   jmp sysexit
+   dac u.pid			" set child pid
+   isz 9f+t			" advance to second word in process table
+   dac 9f+t i			" set pid in process table
+   isz u.rq+8			" give skip return
+   dzm u.intflg			" clear int flag
+   jmp sysexit			" return in child process
 t= t+1
 
-badcal:
-   clon
+badcal:				" bad (unimplemented) system call
+   clon				" clear any pending clock interrupt?
    -1
-   dac 7
-.save:
-   lac d1
+   dac 7			" set location 7 to -1?!
+	" fall into "save" system call
+	" Ken says save files could be resumed, and used for checkpointing!
+.save:				" "sys save" system call
+   lac d1			" get inode 1 (core file?)
    jms iget
    cla
-   jms iwrite; 4096; 4096
-   jms iwrite; userdata; 64
+   jms iwrite; 4096; 4096	" dump core
+   jms iwrite; userdata; 64	" and user area
    jms iput
 
 .exit:
    lac u.dspbuf
-   sna
-   jmp .+3
-   law dspbuf
-   jms movdsp
+   sna				" process using display?
+   jmp .+3			"  no
+   law dspbuf			"   yes
+   jms movdsp			"   move display
    jms awake
    lac u.ulistp i
-   and o77777
+   and o77777			" mark process table entry free
    dac u.ulistp i
    isz u.ulistp
-   dzm u.ulistp i
-   jms swap
+   dzm u.ulistp i		" clear pid in process table
+   jms swap			" find a new process to run
 
 .rmes:
    jms awake
@@ -124,25 +140,28 @@ badcal:
 t = t+1
 
 "** 01-s1.pdf page 16
+	" smes system call
+	" AC/ pid
+	"   sys smes
 .smes:
-   lac u.ac
-   sna spa
-   jms error
-   jms searchu; 1f
+   lac u.ac			" get pid from user AC
+   sna spa			" >0?
+   jms error			"  no: error
+   jms searchu; 1f		" search for process
    law 2
    tad u.ulistp
    dac 9f+t
    dzm 9f+t i
    jms error
-1: 0
-   lac lu+1
-   sad u.ac
-   skp
-   jmp 1b i
-   lac lu+2
-   sad dm1
-   jmp 1f
-   lac o100000
+1: 0				" worker for searchu
+   lac lu+1			" get pid
+   sad u.ac			" match?
+   skp				"  yes
+   jmp 1b i			"   no
+   lac lu+2			" get mailbox
+   sad dm1			" -1?
+   jmp 1f			"  yes
+   lac o100000			" no: increment process status
    tad u.ulistp i
    dac u.ulistp i
    law 2
@@ -177,19 +196,19 @@ t = t+1
 awake: 0
    jms searchu; 1f
    jmp awake i
-1: 0
-   lac u.pid
-   sad lu+2
-   skp
-   jmp 1b i
+1: 0				" searchu worker
+   lac u.pid			" get caller pid
+   sad lu+2			" match process table entry?
+   skp				"  yes
+   jmp 1b i			"   no, return
    -3
-   tad 8
-   dac 9f+t
+   tad 8			" get pointer to pid in process table??
+   dac 9f+t			" save in t0
 "** 01-s1.pdf page 17
-   lac o700000
+   lac o700000			" set high bits
    tad 9f+t i
    dac 9f+t i
-   jmp 1b i
+   jmp 1b i			" return from worker
 t = t+1
 
 swr:
@@ -200,15 +219,16 @@ sww:
 
 .halt: jms halt
 
+	" read routine for ttyin special file
 rttyi:
    jms chkint1
    lac d1
    jms getchar
       jmp 1f
    and o177
-   jms betwen; o101; o132
-      skp
-   tad o40
+   jms betwen; o101; o132	" upper case?
+      skp			"  no
+   tad o40			"   yes: convert to lower
    alss 9
    jmp passone
 1:
@@ -216,6 +236,7 @@ rttyi:
    jms swap
    jmp rttyi
 
+	" write routine for ttyout special file
 wttyo:
    jms chkint1
    jms forall
@@ -243,6 +264,7 @@ wttyo:
    jms swap
    jmp wttyo
 
+	" read routine for (display) "keyboard" special file
 rkbdi:
    jms chkint1
    lac d3
@@ -282,6 +304,7 @@ rkbdi:
    jms swap
    jmp rkbdi
 
+	" write routine for (graphic) "display" special file
 wdspo:
    jms chkint1
    jms forall
@@ -292,6 +315,7 @@ wdspo:
    jmp wdspo
 
 
+	" read routine for paper tape reader special file
 rppti:
    lac d4
    jms getchar
@@ -307,6 +331,7 @@ rppti:
    jmp rppti
 "** 01-s1.pdf page 19
 
+	" write routine for paper tape punch special file
 wppto:
    jms forall
    sna
@@ -331,6 +356,7 @@ wppto:
    jms swap
    jmp wppto
 
+	" common exit for special file
 passone:
    sad o4000
    jmp okexit
diff --git a/pdp7parse/src/test/resources/s4.s b/pdp7parse/src/test/resources/s4.s
new file mode 100644
index 0000000..5d37eec
--- /dev/null
+++ b/pdp7parse/src/test/resources/s4.s
@@ -0,0 +1,371 @@
+"** 01-s1.pdf page 21
+" s4
+
+	" allocate a free disk block for a file (data or indirect)
+alloc: 0
+   -1
+   tad s.nfblks
+   spa
+   jmp 1f
+   dac s.nfblks
+   tad fblksp
+   jms laci
+   dac 9f+t
+   jms copyz; dskbuf; 64
+   lac 9f+t
+   jms dskwr
+   dzm .savblk
+   lac 9f+t
+   jmp alloc i
+1:
+   lac s.nxfblk
+   sna
+   jms halt " OUT OF DISK
+   dac s.fblks
+   jms dskrd
+   lac dskbuf
+   dac s.nxfblk
+   jms copy; dskbuf+1; s.fblks+1; 9
+   lac d10
+   dac s.nfblks
+   jmp alloc+1
+
+	" free a disk block
+free: 0
+   lmq
+   lac s.nfblks
+   sad d10
+   jmp 1f
+   tad fblksp
+   dac 9f+t
+   lacq
+   dac 9f+t i
+   dzm .savblk
+   isz s.nfblks
+   jmp free i
+1:
+   lac s.nxfblk
+   dac dskbuf
+   jms copy; s.fblks+1; dskbuf+1; 9
+   lacq
+   dac s.nxfblk
+   jms dskwr
+   dzm .savblk
+   lac d1
+   dac s.nfblks
+   jmp free i
+t = t+1
+
+	" load AC indirect (without using indirect!)
+	" AC/ address
+	"   jms laci
+	" AC/ contents of address
+laci: 0
+   and o17777				" clear everything but addr
+   tad o200000				" make into "lac addr"
+   dac .+1
+   lac ..				" fetch
+   jmp laci i				" return
+
+"** 01-s1.pdf page 22
+
+	" skip if AC between two values (inclusive)
+	"   jms betwen; low_ptr; high_ptr
+	"    <not between>
+	"  <between>
+	" listing has an alternate written in
+	"  (which would require 'lac ptr' instead of 'ptr' args?)
+betwen: 0
+   lmq cmq			" get ~AC in MQ
+   lac betwen i			" get low_ptr
+   dac 9f+t
+   isz betwen			" skip low_ptr
+   lacq				" get ~AC (-AC-1) from MQ
+   tad 9f+t i			" get low-AC-1
+   sma				" negative (AC >= low)?
+   jmp 1f			"  no, return w/o skip
+   lac betwen i			" fetch high_ptr
+   dac 9f+t
+   isz betwen			" skip high_ptr
+   lacq				" get -AC-1
+   tad 9f+t i			" add to high value (high-AC-1)
+   cma				" complement (AC-high)
+   spa sna			" AC-high <= 0?
+1:
+   isz betwen			"  no: give happy (skip) return
+   lacq				" restore ~AC
+   cma				" restore AC
+   jmp betwen i			" return w/o skip
+
+	" copy memory
+	" call:
+	"   jms copy; src; dest; count
+copy: 0
+   -1
+   tad copy i
+   dac 8
+   isz copy
+   -1
+   tad copy i
+   dac 9
+   isz copy
+   -1
+   tad copy i
+   cma
+   dac 9f+t
+   isz copy
+1:
+   lac 8 i
+   dac 9 i
+   isz 9f+t
+   jmp 1b
+   jmp copy i
+
+	" copy zeroes (clear memory)
+	" call:
+	"   jms copyz; pointer; count
+copyz: 0
+   -1
+   tad copyz i			" get call PC
+   dac 8			" save in index (pre-increments)
+   isz copyz			" skip pointer
+   -1
+   tad copyz i			" get count-1
+   cma				" get negative count
+   dac 9f+t			" save in t0
+   isz copyz			" skip count
+1:
+   dzm 8 i			" zero word
+   isz 9f+t			" done?
+   jmp 1b			"  no: loop
+   jmp copyz i			" return
+t = t+1
+
+putchar: 0
+"** 01-s1.pdf page 23
+   dac 9f+t
+   cla
+   jms takeq
+      jmp putchar i
+   tad o40001
+   dac .+4
+   lac 9f+t
+   jms putq
+   lac char
+   dac q2+1 ..
+   isz putchar
+   jmp putchar i
+t = t+1
+
+getchar: 0
+   jms takeq
+      jmp i getchar
+   tad o200001
+   dac .+3
+   cla
+   jms putq
+   lac q2+1 ..
+   isz getchar
+   jmp i getchar
+
+takeq: 0
+   rcl
+   tad lacq1
+   dac .+7
+   tad o640000
+   dac .+17
+   tad d1
+   dac .+14
+   tad o500000
+   dac .+5
+   lac q1 ..
+   sna
+   jmp takeq i
+   dac lnkaddr
+   sad q1+1 ..
+   jmp .+5
+   tad o200000
+   dac .+1
+   lac q2 ..
+   jmp .+3
+   cla
+   dac q1+1 ..
+   dac q1 ..
+   isz takeq
+   lac lnkaddr
+   jmp i takeq
+
+putq: 0
+   rcl
+   tad dacq1
+   dac .+14
+   tad d1
+   dac .+13
+   tad o140000
+   dac .+1
+   lac q1-1 ..
+"** 01-s1.pdf page 24
+   sna
+   jmp .+6
+   tad o40000
+   dac .+2
+   lac lnkaddr
+   dac q2 ..
+   jmp .+3
+   lac lnkaddr
+   dac q1 ..
+   dac q1+1 ..
+   jmp putq i
+
+srcdbs: 0
+   dac 9f+t+2   "* lmq
+   -ndskbs
+   dac 9f+t
+   law dskbs	"* -1 dac 8 written
+   dac 9f+t+1	"* lacq
+1:
+   lac 9f+t+2	"** crossed out
+   sad 9f+t+1	"** isz 8 written
+   jmp srcdbs i
+   law 65	"** ??? crossed out
+   tad 9f+t+1	"** crossed out isz 8 written
+   isz 9f+t+1
+   isz 9f+t
+   jmp 1b
+   isz srcdbs
+   jmp srcdbs i
+
+collapse: 0
+   cla
+   jms srcdbs
+      jmp 1f
+   law dskbs
+   dac 9f+t+1	"** 9f+t+1 crossed out: 8 written in
+1:
+   lac 9f+t+1	"** 9f+t+1 crossed out: 8 written in
+   dac 0f+1
+   tad d65	"** crossed out: d2-- original obscured
+   dac 0f
+   cma
+   tad d1
+   tad edskbsp
+   and o17777
+   sna
+   jmp 0f+3
+   dac 0f+2
+   jms copy; 0:..; ..; ..
+   -65
+   tad edskbsp
+   dac 9f+t
+   tad d1
+   dac 0f
+   lac dskaddr
+   dac 9f+t i
+   jms copy; dskbuf; 0:..; 64
+   jmp collapse i
+
+dskrd: 0
+   jms betwen; d2; d7999
+
+"** 01-s1.pdf page 25
+      jms halt
+   sad dskaddr
+   jmp dskrd i
+   dac dskaddr
+   jms srcdbs
+      jmp 1f
+   lac dskaddr
+   jms dskio; 06000
+   jmp 2f
+1:
+   dzm 9f+t+1 i
+   law 1
+   tad 9f+t+1
+   dac .+2
+   jms copy; ..; dskbuf; 64
+2:
+   jms collapse
+   jmp dskrd i
+
+	" write a file block (data, inode or indirect)
+	" AC/ block
+dskwr: 0
+   jms betwen; d2; d7999
+      jms halt
+   jms dskio; 07000
+   lac dskaddr
+   jms srcdbs
+      dzm 9f+t+1 i
+   jms collapse
+   jmp dskwr i
+t = t+3
+
+	" AC/ block
+	"   jms dskio; dsld_bits
+dskio: 0
+   dac dskaddr
+   cll; idiv; 80
+   dac 9f+t
+   lacq
+   idiv; 10
+   dac 9f+t+1
+   lls 22
+   xor 9f+t+1
+   als 8
+   dac 9f+t+1
+   lac 9f+t
+   idiv; 10
+   dac 9f+t
+   lls 22
+   xor 9f+t
+   xor 9f+t+1
+   xor o200000
+   dac 9f+t
+   jms dsktrans; -64; dskbuf; 9f+t; dskio
+   isz dskio
+   jmp dskio i
+t = t+1
+
+	" called with:
+	"   jms dsktrans; -WC; MAC; addr_ptr?; dsld_ptr
+dsktrans: 0
+   -10
+   dac 9f+t
+1:
+   -1
+   tad dsktrans
+   dac 12
+"** 01-s1.pdf page 26
+   dscs				" clear status register
+   lac 12 i
+   dslw				" load WC
+   lac 12 i
+   dslm				" load MAC
+   lac 12 i
+   jms laci
+   dsld				" load TA & SA
+   dzm .dskb
+   lac 12 i
+   jms laci
+   jms laci
+   dsls				" load status
+   lac .dskb			" check for interrupt
+   sna
+   jmp .-2
+   lac .dske			" get status from interrupt
+   sma
+   jmp 12 i			" return
+   isz 9f+t
+   jmp 1b
+   jms halt " 10 disk errors
+t = t+1
+
+halt: 0
+   isz 9f+t			" spin for a while (process interrupts)
+   jmp .-1
+   iof				" disable interrupts
+   hlt				" halt
+   jms copy; law; 4096; 4096	" continued: copy system up to user memory?
+   hlt; jmp .-1			" halt for good
+t = t+1
+
diff --git a/pdp7parse/src/test/resources/s5.s b/pdp7parse/src/test/resources/s5.s
index 6c89ab9..f83f6e8 100644
--- a/pdp7parse/src/test/resources/s5.s
+++ b/pdp7parse/src/test/resources/s5.s
@@ -1,75 +1,86 @@
 "** 01-s1.pdf page 28
 " s5
-
+	" read/write a process from/to swap space
+	" call:
+	" AC/ first word of process table
+	"   jms dskswap; DSLD bits
 dskswap: 0
-   cll; als 3
-   dac 9f+t
-   jms dsktrans; -64; userdata; 9f+t; dskswap
-   lac 9f+t
-   tad o20
-   dac 9f+t
-   jms dsktrans; -4096; 4096; 9f+t; dskswap
-   isz dskswap
-   jmp dskswap i
+   cll; als 3			" get process disk address
+   dac 9f+t			" save in t0
+   jms dsktrans; -64; userdata; 9f+t; dskswap	" read/write user area
+   lac 9f+t			" get swap addr back
+   tad o20			" advance by 16??
+   dac 9f+t			" save
+   jms dsktrans; -4096; 4096; 9f+t; dskswap	" read/write user memory
+   isz dskswap			" skip bits
+   jmp dskswap i		" return
 t = t+1
 
 access: 0
    lac i.flags
-   lmq
-   lac u.uid
-   spa
-   jmp access i
-   sad i.uid
-   lrs 2
-   lacq
-   and mode
-   sza
-   jmp access i
-   jms error
+   lmq				" save in MQ
+   lac u.uid			" get user id
+   spa				" negative?
+   jmp access i			"  yes: super user, return
+   sad i.uid			" compare to file owner
+   lrs 2			"  same: shift flags down two
+   lacq				" get flags back
+   and mode			" mode from system call
+   sza				" access allowed?
+   jmp access i			"  yes: return
+   jms error			" no: return error from system call
 
 fassign: 0
-   -10
-   dac 9f+t
+   -10				" loop count
+   dac 9f+t			" in t0
 1:
-   lac 9f+t
-   tad d10
-   jms fget
+   lac 9f+t			" get count
+   tad d10			" turn into fd
+   jms fget			" fetch open file into "fnode"
       jms halt " will not happen
-   lac f.flags
-   sma
-   jmp 1f
-   isz 9f+t
+   lac f.flags			" get fnode flags
+   sma				" sign bit set (active)?
+   jmp 1f			"  no: free
+   isz 9f+t			" increment loop count & loop until zero
    jmp 1b
    jmp fassign i
 1:
-   lac mode
-   xor o400000
-   dac f.flags
-   lac ii
-   dac f.i
+   lac mode			" get mode from system call
+   xor o400000			" set sign bit
+   dac f.flags			" save in fnode
+   lac ii			" get i-number
+   dac f.i			" save in fnode
    lac 9f+t
-   tad d10
-   dac u.ac
-   dzm f.badd
-   jms fput
-   isz fassign
+   tad d10			" get fd
+   dac u.ac			" return in user AC
+   dzm f.badd			" clear file offset in fnode
+   jms fput			" copy fnode back into u.ofiles
+   isz fassign			" give skip return
    jmp fassign i
 t = t+1
 
+	" load fnode (open file entry) from u.ofiles
+	" AC/ user fd
+	"   jms fget
+	"    bad fd
+	"   return with fnode set
 fget: 0
-   jms betwen; d0; d9
-      jmp fget i
-   cll; mul; 3
+   jms betwen; d0; d9		" fd 0..9?
+      jmp fget i		"  no, return
+   cll; mul; 3			" multiply by three
    lacq
 "** 01-s1.pdf page 29
 
-   tad ofilesp
-   dac 9f+t
-   dac .+2
-   jms copy; ..; fnode; 3
-   isz fget
+   tad ofilesp			" get pointer into u.ofiles
+   dac 9f+t			" save in t0
+   dac .+2			" save as copy source
+   jms copy; ..; fnode; 3	" copy to "fnode"
+   isz fget			" give skip return
    jmp fget i
 
+	" copy fnode back to u.ofiles
+	" uses temp value set by "fget"
+	" (fget and fput calls must be paired)
 fput: 0
    lac 9f+t
    dac .+3
@@ -138,6 +149,8 @@ dslot: 0
    jmp 1b
    jmp dslot i
 
+	" called with:
+	" AC/ mode
 icreat: 0
    dac 9f+t
    jms dslot
diff --git a/pdp7parse/src/test/resources/s6.s b/pdp7parse/src/test/resources/s6.s
index 0072349..f1d07be 100644
--- a/pdp7parse/src/test/resources/s6.s
+++ b/pdp7parse/src/test/resources/s6.s
@@ -2,41 +2,41 @@
 " s6
 
 itrunc: 0
-   -7
-   dac 9f+t
-   lac idskpp
-   dac 9f+t+1
-1:
-   lac 9f+t+1 i
-   sna
-   jmp 4f
+   -7					" loop 7 times
+   dac 9f+t				" in t0
+   lac idskpp				" pointer to inode block numbers
+   dac 9f+t+1				" save in t1
+1:			" top of loop for inode blocks
+   lac 9f+t+1 i				" fetch next block number
+   sna					" allocated?
+   jmp 4f				"  no
+   lac i.flags				" check flags
+   and o200000				
+   sna					" large file?
+   jmp 3f				"  no
+   -64					" loop 64 times
+   dac 9f+t+2				" save count in t2
+   lac dskbufp				" get pointer to dskbuf
+   dac 9f+t+3				" in t3
+2:			" inner loop for indirect blocks
+   lac 9f+t+1 i				" get indirect block number
+   jms dskrd				" read it
+   lac 9f+t+3 i				" read block number from indirect
+   sza					" free?
+   jms free				"  no: free it
+   isz 9f+t+3				" increment pointer into indirect block
+   isz 9f+t+2				" increment loop counter, skip if done
+   jmp 2b				"  not done: loop
+3:			" here with small file
+   lac 9f+t+1 i				" load block number
+   jms free				" free it
+   dzm 9f+t+1 i				" clear block number
+4:			" bottom of loop for inode block ptrs
+   isz 9f+t+1				" increment block pointer
+   isz 9f+t				" increment count, skip if done
+   jmp 1b				"  not done
    lac i.flags
-   and o200000
-   sna
-   jmp 3f
-   -64
-   dac 9f+t+2
-   lac dskbufp
-   dac 9f+t+3
-2:
-   lac 9f+t+1 i
-   jms dskrd
-   lac 9f+t+3 i
-   sza
-   jms free
-   isz 9f+t+3
-   isz 9f+t+2
-   jmp 2b
-3:
-   lac 9f+t+1 i
-   jms free
-   dzm 9f+t+1 i
-4:
-   isz 9f+t+1
-   isz 9f+t
-   jmp 1b
-   lac i.flags
-   and o577777
+   and o577777				" clear large file flag
    dac i.flags
    jmp itrunc i
 t = t+4
@@ -185,100 +185,107 @@ dput: 0
 
 t = t+3
 
+	" allocate a block for a file, returns disk block number
+	" AC/ file offset
+	"   jms pget
+	" AC/ disk block number
 pget: 0
-   lrss 6
-   dac 9f+t
+   lrss 6				" convert offset to block
+   dac 9f+t				" save as t0
    lac i.flags
 
 "** 01-s1.pdf page 37
 
    and o200000
-   sza
-   jmp 2f
-   lac 9f+t
-   jms betwen; d0; d6
-      jmp 1f
-   tad idskpp
-   dac 9f+t
-   lac 9f+t i
-   sna
-   jms alloc
-   dac 9f+t i
-   jmp pget i
-1:
-   jms alloc
-   dac 9f+t+1
-   jms copy; i.dskps; dskbuf; 7
-   jms copyz; dskbuf+7; 64-7
+   sza					" large file bit set?
+   jmp 2f				"  yes
+   lac 9f+t				" no: small file
+   jms betwen; d0; d6			" block 0..6?
+      jmp 1f				"  no
+   tad idskpp				" make into block number pointer
+   dac 9f+t				" save in t0
+   lac 9f+t i				" get disk block number
+   sna					" allocated?
+   jms alloc				"  no: allocate now
+   dac 9f+t i				" save (new) disk block number
+   jmp pget i				" return disk block number
+1:					" here when file block>=7, not "large"
+   jms alloc				" allocate indirect block
+   dac 9f+t+1				" save as t1
+   jms copy; i.dskps; dskbuf; 7		" copy all the disk block numbers
+   jms copyz; dskbuf+7; 64-7		" zero rest of indirect block
+   lac 9f+t+1				" get indirect block number back
+   jms dskwr				" write indirect block to disk
    lac 9f+t+1
-   jms dskwr
-   lac 9f+t+1
-   dac i.dskps
-   jms copyz; i.dskps+1; 6
+   dac i.dskps				" save indirect as new first block
+   jms copyz; i.dskps+1; 6		" zero rest of block pointers
    lac i.flags
-   xor o200000
+   xor o200000				" set "large file"
    dac i.flags
-2:
-   lac 9f+t
-   lrss 6
-   jms betwen; d0; d6
-      jms halt " file too big
-   tad idskpp
-   dac 9f+t+1
-   lac 9f+t+1 i
-   sna
-   jms alloc
-   dac 9f+t+1 i
-   dac 9f+t+2
-   jms dskrd
-   lac 9f+t
-   and o77
-   tad dskbufp
-   dac 9f+t+1
-   lac 9f+t+1 i
-   sza
-   jmp pget i
-   jms alloc
-   dac 9f+t
+2:					" here with "large file"
+   lac 9f+t				" get file block number
+   lrss 6				" divide by 64 (indirects/block)
+   jms betwen; d0; d6			" ok now?
+      jms halt " file too big		"  no, you lose!
+   tad idskpp				" yes: get indirect block pointer
+   dac 9f+t+1				" save in t1
+   lac 9f+t+1 i				" get indirect block number
+   sna					" allocated?
+   jms alloc				"  no, get it now
+   dac 9f+t+1 i				" save (new) indirect block
+   dac 9f+t+2				" save as t2
+   jms dskrd				" read indirect block
+   lac 9f+t				" get original block number
+   and o77				" mod by 64
+   tad dskbufp				" get pointer to disk block number
+   dac 9f+t+1				" save as t1
+   lac 9f+t+1 i				" fetch disk block number
+   sza					" allocated?
+   jmp pget i				"  yes: return
+   jms alloc				" no: allocate data block
+   dac 9f+t				" save as t0
+   lac 9f+t+2				" get indirect block number
+   jms dskrd				" read it in
+   lac 9f+t				" get data block number
+   dac 9f+t+1 i				" save data block number
    lac 9f+t+2
-   jms dskrd
-   lac 9f+t
-   dac 9f+t+1 i
-   lac 9f+t+2
-   jms dskwr
-   lac 9f+t
-   jmp pget i
+   jms dskwr				" write indirect block back
+   lac 9f+t				" get data block back
+   jmp pget i				" return it
 t = t+3
 
 iwrite: 0
-   dac 9f+t
-   lac iwrite
+   dac 9f+t				" save arg in t0
+   lac iwrite				" load return address
 
 "** 01-s1.pdf page 38
 
-   dac iread
-   lac cskp
-   dac iwrite
+   dac iread				" save as iread return addr
+   lac cskp				" load skip instruction
+   dac iwrite				" save as iwrite instruction
    jmp 1f
 
+	" iread from file referenced by loaded inode
+	" AC/ file offset
+	"    jms iread; addr; count
 iread: 0
-   dac 9f+t
-   lac cnop
-   dac iwrite
+   dac 9f+t				" save offset in t0
+   lac cnop				" get nop
+   dac iwrite				" save as iwrite instruction
 1:
    -1
-   tad iread i
-   dac 10
+   tad iread i				" get word before return addr
+   dac 10				" store in index 10 & 11
    dac 11
-   isz iread
-   lac iread i
-   dac 9f+t+1
-   isz iread
+   isz iread				" increment return addr
+   lac iread i				" load addr
+   dac 9f+t+1				" save in t1
+   isz iread				" increment return addr
    lac o70000
-   xct iwrite
-   lac i.size
+   xct iwrite				" skip if write
+   lac i.size				"  read: get file size
    cma
-   tad 9f+t
+   tad 9f+t				" add offset
    cma
    jms betwen; d0; 9f+t+1
       lac 9f+t+1
@@ -332,6 +339,11 @@ cskp:
    jmp 1b
 t = t+4
 
+	" system call helper
+	" AC/ fd
+	"   jms finac
+	" return with: fnode and inode loaded
+	"	or makes error return to user
 finac: 0
    lac u.ac
    jms fget
@@ -343,6 +355,7 @@ finac: 0
    jms iget
    jmp finac i
 
+	" update inode file size with value in AC
 dacisize: 0
    dac i.size
    jms iput
diff --git a/pdp7parse/src/test/resources/s7.s b/pdp7parse/src/test/resources/s7.s
new file mode 100644
index 0000000..81034bb
--- /dev/null
+++ b/pdp7parse/src/test/resources/s7.s
@@ -0,0 +1,372 @@
+"** 01-s1.pdf page 41
+" s7
+
+pibreak:			" priority interrupt break processing "chain"
+   dac .ac			" save interrupt AC
+	"** CROSSED OUT....
+
+   dpsf
+   jmp 1f
+
+   dpcf
+   dprs
+   dac dpstat
+   sma ral
+   jmp 2f
+   dprc
+   dac dpchar
+   -1
+   dac dpread
+   lac dpstat
+   ral
+2:
+   sma
+   jmp piret
+   -1
+   dac dpwrite
+   jmp piret	"** END OF CROSSOUT
+
+1: clsf			" clock overflow (line frequency ticks)?
+   jmp 1f		"  no
+
+   lpb			" load display push buttons
+   dac pbsflgs		" save
+   isz s.tim+1		" increment low order tick count
+   skp			"  no overflow, skip second increment
+   isz s.tim		"   low order overflowed, increment high order count
+   isz uquant		"    increment user quantum counter
+	"** written: ttydelay -> ttyd1
+	"** written: ttyrestart -> ttyres1
+
+	" referenced in iread:
+cnop:
+   nop
+   -1
+   dac 7		" set location 7 to -1
+   clon			" enable clock interrupts, reset flag
+   lac ttydelay
+   spa
+   isz ttydelay
+   skp
+   jms ttyrestart
+   lac .dspb	"** START CROSSED OUT: written: lac tty
+   sna
+   jmp piret
+   isz .dsptm
+   skp
+   jmp dsprestart
+   sad d3
+   jmp piret
+   isz .dspb
+   jmp piret
+   jmp dsprestart "** END CROSSED OUT
+
+1: dssf
+   jmp 1f
+
+   -1
+   dac .dskb
+
+"** 01-s1.pdf page 42
+
+   dsrs
+   dac .dske
+   dscs
+   jmp piret
+
+1: lds		"** BEGIN CROSSED OUT
+   sma ral
+   jmp 1f
+   cdf
+   lac .dspb
+   sna
+   jmp piret
+   tad dm3
+   sna
+   jmp dsprestart
+   dac .dspb
+   jmp piret
+dsprestart:
+   lac d1
+   dac .dspb
+   lac dspbufp
+   beg
+   -10
+   dac .dsptm
+   jmp piret
+
+1: sna ral
+   jmp .+3
+   dpcf
+   jmp piret
+   sma
+   jmp 1f
+   lda
+   dac .lpba
+   rlpd
+   jmp piret
+
+1: ksf			" (TTY) keyboard flag set?
+   jmp 1f		"  no
+
+   lac ttydelay
+   sma
+   isz ttydelay
+   krb			" read keyboard buffer
+   dac char		" save in char
+   sad o375		" interrupt char ('}'?)
+   jmp intrp1		"  yes
+   lac d1
+   jms putchar
+      dzm char
+   lac sfiles+0
+   jms wakeup
+   dac sfiles+0
+   lac char
+   sad o212
+   skp
+   jmp piret
+   lac sfiles+1
+   sma
+   xor o400000
+   dac sfiles+1
+
+"** 01-s1.pdf page 43
+
+   jms putcr
+   jms ttyrestart
+   jmp piret
+
+1: tsf
+   jmp 1f
+
+   tcf
+   jms ttyrestart
+   jmp piret
+
+ttyrestart: 0
+   lac ttydelay
+   spa
+   jmp ttyrestart i
+   lac nttychar
+   dzm nttychar
+   sza
+   jmp 3f
+   isz ttydelay
+   lac d2
+   jms getchar
+      jmp 2f
+3:
+   tls
+   sad o12
+   jms putcr
+   sad o15
+   skp
+   jmp ttyrestart i
+   lac ttydelay
+   tad o20
+   rcr
+   cma
+   dac ttydelay
+   jmp ttyrestart i
+2:
+   lac sfiles+1
+   jms wakeup
+   dac sfiles+1
+   jmp ttyrestart i	"** written arrow up 2 copies
+
+			"** BEGIN CROSSED OUT
+1: sck				" Graphic-2 keyboard flag set?
+   jmp 1f			"  no.
+
+   cck				" yes: clear flag
+   lck				" read character
+   dac char
+   sad o33			" code 33 (ESCAPE?)
+   jmp intrp2			"  yes: mark interrupt
+   lac d3
+   jms putchar
+      nop
+   lac sfiles+2
+   jms wakeup
+   dac sfiles+2
+   jmp piret
+
+1: rsf				" paper tape ready?
+   jmp 1f			"  no
+
+
+"** 01-s1.pdf page 44
+
+   lac npptchar
+   sna
+   jmp .+5
+   dac char
+   rrb
+   dac npptchar
+   jmp .+3
+   rrb
+   dac char
+3:
+   lac char
+   sna
+   jmp 2f
+   lac d4
+   jms putchar
+      jmp 3f
+   lac char
+   sad d4
+   jmp 4f
+2:
+   lac npptchar
+   sna
+   jmp .+4
+   dac char
+   dzm npptchar
+   jmp 3b
+   rsa
+   lac sfiles+3
+   jms wakeup
+   xor o400000
+   dac sfiles+3
+   jmp piret
+3:
+   lac char
+   dac npptchar
+4:
+   lac sfiles+3
+   jms wakeup
+   dac sfiles+3
+   jmp piret
+
+1: psf					" paper tape ready?
+   jmp 1f				"  no
+
+   pcf					" clear ptp flag
+   lac d5
+   jms getchar				" get next char
+   jmp .+3
+   psa
+   jmp piret
+   lac sfiles+4
+   jms wakeup
+   dac sfiles+4
+   jmp piret
+
+		"** BEGIN CROSSED OUT
+1: spb					" graphic 2 push button flag set?
+   jmp 1f				"  no
+
+   cpb					" clear push button flag
+   lpb					" load push button value
+   dac pbsflgs+1
+
+"** 01-s1.pdf page 45
+
+   and o2000
+   sna
+   jmp piret
+   jms dspinit
+   lac sfiles+6
+   jms wakeup
+   dac sfiles+6
+   cla
+   wbl
+   jmp piret	"** END CROSSED OUT
+
+1: crsf					" card reader flag set?
+   jmp 1f				"  no
+
+   crrb
+   dac crchar
+   -1
+   dac crread
+   jmp piret
+
+1: crrb					" read card reader buffer??
+
+piret:					" return from priority interrupt
+   lac 0				" get LINK/PC
+   ral					" restore LINK
+   lac .ac				" restore AC
+   ion					" reenable interrupts
+   jmp 0 i				" return from interrupt
+
+wakeup: 0
+   dac 9f+t
+   -mnproc
+   dac 9f+t+1
+   lac tadu
+   dac 2f
+   lac dacu
+   dac 2f+1
+1:
+   lac 9f+t
+   ral
+   dac 9f+t
+   sma
+   jmp 2f+2
+   lac o700000
+2: tad ..
+   dac ..
+   lac 2b
+   tad d4
+   dac 2b
+   lac 2b+1
+   tad d4
+   dac 2b+1
+   isz 9f+t+1
+   jmp 1b
+   cla
+   jmp wakeup i
+t = t+2
+
+putcr: 0
+   lac o15
+   dac nttychar
+
+"** 01-s1.pdf page 46
+
+   cla
+   jmp putcr i
+
+intrp1:			" here with keyboard interrupt
+   lac d6		" get keyboard special device number
+   dac .int1		" save as interrupt source
+   lac d1
+   jms getchar
+      skp
+   jmp .-3
+   lac d2
+   jms getchar
+      skp
+   jmp .-3
+   lac sfiles+0
+   jms wakeup
+   dac sfiles+0
+   lac sfiles+1
+   jms wakeup
+   dac sfiles+1
+   jms chkint
+      jmp piret
+   jmp 1f
+intrp2:
+   lac d7
+   dac .int2
+   lac d3
+   jms getchar
+      skp
+   jmp .-3
+   lac sfiles+2
+   jms wakeup
+   dac sfiles+2
+   lac sfiles+6
+   jms wakeup
+   dac sfiles+6
+   jms chkint
+      jmp piret
+1:
+   lac 0
+   dac 020
+   lac .ac
+   jmp 021
diff --git a/pdp7parse/src/test/resources/s8.s b/pdp7parse/src/test/resources/s8.s
index 7a60623..afce88c 100644
--- a/pdp7parse/src/test/resources/s8.s
+++ b/pdp7parse/src/test/resources/s8.s
@@ -8,14 +8,15 @@ dspbsz = 270
 ndskbs = 4
 
 " flags
-.insys: 0
-.int1: 0
-.int2: 0
-.ac: 0
-.savblk: 0
-.dsptm: 0
-.dskb: 0
-.dske: 0
+	" interupt flags
+.insys: 0			" "in system"
+.int1: 0			" inode for interrupt 1
+.int2: 0			" inode for interrupt 2
+.ac: 0				" saved AC from interrupt
+.savblk: 0			" set by system call, cleared by disk i/o
+.dsptm: 0			" display restart countdown (10 ticks)
+.dskb: 0			" set on disk interrupt
+.dske: 0			" status from disk interrupt
 
 " pointers
 tadu: tad ulist
@@ -110,25 +111,25 @@ dspbuf:
    .=.+30
 coldentry:
    dzm 0100 " not re-entrant
-   caf
-   ion
-   clon
-   law 3072
+   caf				" clear all flags
+   ion				" enable interrupts
+   clon				" clear clock flag
+   law 3072			" initialize display....
    wcga
    jms dspinit
    law dspbuf
    jms movdsp
-   cla
+   cla				" read system block from disk
    jms dskio; 06000
-   jms copy; dskbuf; sysdata; ulist-sysdata
-   lac d3
+   jms copy; dskbuf; sysdata; ulist-sysdata	" copy to system data
+   lac d3			" look for "init" in default directory
    jms namei; initf
       jms halt
 "** 01-s1.pdf page 50
    jms iget
    cla
-   jms iread; 4096; 4096
-   jmp 4096
+   jms iread; 4096; 4096	" read in "init"
+   jmp 4096			" start process 1
    . = dspbuf+dspbsz+3
 dskbuf = 07700
 dskbs: .=.+65+65+65+65
@@ -144,9 +145,9 @@ name: .=.+4
 lnkaddr: .=.+1
 char: .=.+1
 dskaddr: .=.+1
-uniqpid: 1
-lu: .=.+4
-sfiles: .=.+10
+uniqpid: 1			" pid generator
+lu: .=.+4			" user (process) table entry copy
+sfiles: .=.+10			" wait addresses for special files
 dpdata:
    dpstat: .=.+1
    dpread: .=.+1
@@ -158,12 +159,24 @@ dspdata:
 crdata:
    crread: .=.+1
    crchar: .=.+1
-sysdata:
-   s.nxfblk: .=.+1
-   s.nfblks: .=.+1
-   s.fblks: .=.+10
-   s.uniq: .=.+1
-   s.tim: .=.+2
+sysdata:			" system data 64 words saved to disk
+   s.nxfblk: .=.+1		" pointer to next free block??
+   s.nfblks: .=.+1		" number of free blocks (in fblks?)
+   s.fblks: .=.+10		" cached free block numbers
+   s.uniq: .=.+1		" next unique value
+   s.tim: .=.+2			" (up?)time in 60Hz ticks (low, high)
+	" process table
+	" first word
+	"   bits 0:2 -- status
+	"	0: free slot
+	"	1: in/ready
+	"	2: in/notready
+	"	3: out/ready
+	"	4: out/notready??
+	"   bits 3:17 -- disk swap address/8
+	" second word: process pid
+	" third word:  used for smes/rmes
+	" fourth word: ??
 ulist:
    0131000;1;0;0
    0031040;0;0;0
@@ -175,40 +188,51 @@ ulist:
    0031340;0;0;0
    0031400;0;0;0
    0031440;0;0;0
-userdata:
-   u.ac: 0
-   u.mq: 0
-   u.rq: .=.+9
-   u.uid: -1
-   u.pid: 1
-   u.cdir: 3
-   u.ulistp: ulist
-   u.swapret: 0
-   u.base: 0
-   u.count: 0
+userdata:			" "ustruct" (swappable)
+   u.ac: 0			" user AC
+   u.mq: 0			" user MQ
+   u.rq: .=.+9			" user 010-017, user PC
+   u.uid: -1			" user id
+   u.pid: 1			" process id
+   u.cdir: 3			" connected directory (inode number?)
+   u.ulistp: ulist		" pointer to process table entry
+   u.swapret: 0			" kernel routine to resume at after swap in
+   u.base: 0			" start of user buffer
+   u.count: 0			" size of user buffer
 "** 01-s1.pdf page 51
-   u.limit: 0
-   u.ofiles: .=.+30
+   u.limit: 0			" end of user buffer
+   u.ofiles: .=.+30		" open files (10 "fnode" entries)
    u.dspbuf: 0
    u.intflg: 1
       .=userdata+64
-ii: .=.+1
-inode:
-   i.flags: .=.+1
-   i.dskps: .=.+7
-   i.uid: .=.+1
-   i.nlks: .=.+1
+ii: .=.+1			" number of i-node in inode:
+inode:				" disk inode in memory:
+   i.flags: .=.+1		" inode flags
+				" 400000 free?? (checked/toggled by icreat)
+				" 200000 large file
+				" 000040 special device (indicated by inum)?
+				" 000020  directory
+				" 000010 owner read
+				" 000004 owner write
+				" 000002 world read
+				" 000001 world write
+   i.dskps: .=.+7		" disk block pointers (indirect if "large file")
+   i.uid: .=.+1			" owner
+   i.nlks: .=.+1		" link count
    i.size: .=.+1
-   i.uniq: .=.+1
+   i.uniq: .=.+1		" unique number
       .= inode+12
 di: .=.+1
-dnode:
-   d.i: .=.+1
-   d.name: .=.+4
-   d.uniq: .=.+1
+dnode:				" directory entry:
+   d.i: .=.+1			" inode number
+   d.name: .=.+4		" name (space padded)
+   d.uniq: .=.+1		" unique number from directory inode
       . = dnode+8
-fnode:
-   f.flags: .=.+1
-   f.badd: .=.+1
-   f.i: 0
-
+fnode:				" open file entry
+   f.flags: .=.+1		" see below
+   f.badd: .=.+1		" offset
+   f.i: 0			" file i-number
+"	f.flags:
+"		400000	in use
+"		000002	read
+"		000001	write