diff --git a/src/rz/factor.26 b/src/rz/factor.26
deleted file mode 100644
index 67cfe891..00000000
--- a/src/rz/factor.26
+++ /dev/null
@@ -1,403 +0,0 @@
-
-TITLE FACTOR
-
-Z=0
-A=1
-B=2
-C=3
-D=4
-E=5
-DV=5
-P=6
-
-.MLLIT==1
-KL10==1		;;KL10 RUNS SLOWER IN ACS
-
-TYIC==1
-TYOC==2
-INFOC==3
-
-PDLL=100
-
-IFE KL10,	LOC 7
-TEST:	TRC .+1,6
-INCR:	ADDI DV,2
-RETEST:	MOVE Z,C
-	MOVE B,D
-	IDIV Z,DV
-	DIV A,DV
-	CAMLE DV,A
-	 JUMPE Z,PRIME
-	JUMPN B,TEST
-	JRST FOUND
-
-IFE KL10,	LOC 100
-GO:	MOVE P,[-PDLL,,PDL]
-	.OPEN TYIC,[0,,(SIXBIT /TTY/)]
-	JRST KILL
-	.OPEN TYOC,[1,,(SIXBIT /TTY/)]
-	JRST KILL
-DECIMA:	MOVEI C,10.
-RADSET:	MOVEM C,RADX'
-RESET:	PUSHJ P,PROMPT
-ZBC:	SETZB B,C
-
-LOOP:	PUSHJ P,TYI
-	ANDI A,177
-	JRST @TYIDIS(A)
-TYIDIS:	HUH	;^@
-	HUH	;^A
-	HUH	;^B
-	HUH	;^C
-	HUH	;^D
-	HUH	;^E
-	HUH	;^F
-	KILL	;^G
-	HUH	;^H
-	HUH	;^I
-	HUH	;^J
-	HUH	;^K
-	HUH	;^L
-	HUH	;^M
-	HUH	;^N
-	HUH	;^O
-	HUH	;^P
-	HUH	;^Q
-	HUH	;^R
-	HUH	;^S
-	HUH	;^T
-	HUH	;^U
-	HUH	;^V
-	HUH	;^W
-	HUH	;^X
-	HUH	;^Y
-	HUH	;^Z
-	HUH	;^[
-	HUH	;^\
-	HUH	;^]
-	HUH	;^^
-	HUH	;^_
-	STM2	;sp
-	HUH	;!
-	HUH	;"
-	HUH	;#
-	HUH	;$
-	HUH	;%
-	HUH	;&
-	HUH	;'
-	HUH	;(
-	HUH	;)
-	TIMES	;*
-	PLUS	;+
-	HUH	;,
-	MINUS	;-
-	HUH	;.
-	DIVIDE	;/
-	NUMBER	;0
-	NUMBER	;1
-	NUMBER	;2
-	NUMBER	;3
-	NUMBER	;4
-	NUMBER	;5
-	NUMBER	;6
-	NUMBER	;7
-	NUMBER	;8
-	NUMBER	;9
-	HUH	;:
-	HUH	;;
-	HUH	;<
-	EQUAL	;=
-	HUH	;>
-	INFO	;?
-
-	HUH	;@
-	HUH	;A
-	HUH	;B
-	CLIST	;C
-	DECIMA	;D
-	HUH	;E
-	FACTOR	;F
-	HUH	;G
-	QUERY	;H
-	HUH	;I
-	HUH	;J
-	HUH	;K
-	LARGE	;L
-	HUH	;M
-	LOAD	;N
-	HUH	;O
-	HUH	;P
-	HUH	;Q
-	RADSET	;R
-	HUH	;S
-	HUH	;T
-	HUH	;U
-	HUH	;V
-	HUH	;W
-	HUH	;X
-	HUH	;Y
-	HUH	;Z
-	HUH	;[
-	HUH	;\
-	HUH	;]
-	POWER	;^
-	HUH	;_
-	HUH	;`
-	HUH	;a
-	HUH	;b
-	CLIST	;c
-	DECIMAL	;d
-	HUH	;e
-	FACTOR	;f
-	HUH	;g
-	QUERY	;h
-	HUH	;i
-	HUH	;j
-	HUH	;k
-	LARGE	;l
-	HUH	;m
-	LOAD	;n
-	HUH	;o
-	HUH	;p
-	HUH	;q
-	RADSET	;r
-	HUH	;s
-	HUH	;t
-	HUH	;u
-	HUH	;v
-	HUH	;w
-	HUH	;x
-	HUH	;y
-	HUH	;z
-	HUH	;{
-	HUH	;|
-	HUH	;}
-	HUH	;~
-	RESET	;rubout
-
-NUMBER:	IMUL B,RADX
-	MUL C,RADX
-	ADDI D,-"0(A)
-	TLZE D,400000
-	AOS C
-	ADD B,C
-	MOVE C,D
-	JRST LOOP
-
-INFO:	PUSHJ P,INFOPN
-	.IOT INFOC,1
-	JUMPL A,RESET
-	CAIE A,3
-	 CAIN A,14
-	  JRST RESET
-	.IOT TYOC,1
-	JRST INFO+1
-
-INFOPN:	.CALL [	SETZ
-		SIXBIT /OPEN/
-		,,[0,,INFOC]
-		,,[SIXBIT /DSK/]
-		,,[SIXBIT /FACTOR/]
-		,,[SIXBIT /ORDER/]
-		400000,,[SIXBIT /.INFO./]]
-	 JRST INFLOS
-CPOPJ:	POPJ P,
-
-INFLOS:	SUB P,[1,,1]
-	MOVE B,[440700,,[ASCIZ \Can't open info file\]]
-	JRST Q3
-
-QUERY:	MOVE B,[440700,,[ASCIZ/elp /]]
-	PUSHJ P,OUT
-	PUSHJ P,INFOPN
-	.IOT TYIC,2
-	PUSHJ P,CR
-	CAIL 2,"0
-	CAILE 2,"9
-	 JRST Q0
-	MOVE 2,[440700,,[ASCIZ/	digit/]]
-	JRST Q3
-Q0:	.IOT INFOC,1
-	JUMPL A,Q1
-	CAIE 1,12	;LINE FEED
-	 JRST Q0
-	.IOT INFOC,1
-	CAME 1,2
-	JRST Q0
-	.IOT INFOC,1
-	JUMPL 1,Q1
-	CAIE 1,11	;TAB
-	JRST Q0
-	JRST .+2
-Q2:	.IOT INFOC,1
-	.IOT TYOC,1
-	CAIE 1,12	;LINE FEED?
-	JRST Q2
-	.IOT INFOC,1
-	CAIN 1,11	;TAB?
-	 JRST Q2+1
-	JRST RESET
-
-CLIST:	SKIPA 2,[440700,,[ASCIZ 7	RD:*;+-/^NLF =QC?7]]
-Q1:	MOVE 2,[440700,,[ASCIZ/	IGNORED/]]
-Q3:	ILDB 1,2
-	JUMPE 1,RESET
-	.IOT 2,1
-	JRST .-3
-
-OUT:	ILDB A,B
-	JUMPE A,CPOPJ
-	.IOT TYOC,A
-	JRST .-3
-
-LOAD:	MOVE B,M1
-	MOVE C,M2
-	JRST LOOP
-
-POWER:	MOVEI Z,-1(C)
-	MOVE A,M2
-	SETZ B,
-	MOVE C,A
-POW1:	IMUL B,A
-	MUL C,A
-	ADD B,C
-	MOVE C,D
-	SOJG Z,POW1
-	JRST STM2
-
-DIVIDE:	MOVE A,C
-	MOVE B,M1
-	MOVE D,M2
-	IDIV B,A
-	DIV C,A
-	JRST STM2
-
-TIMES:	IMUL B,M2
-	MOVE A,C
-	IMUL A,M1
-	MUL C,M2
-	ADD B,C
-	ADD B,A
-	TLZ B,400000
-	MOVEM D,M2
-	MOVEM B,M1
-	JRST ZBC
-
-MINUS:	MOVNS C
-	ADD C,[SETZ]
-	AOS B
-	MOVNS B
-PLUS:	ADD C,M2
-	ADD B,M1
-	TLZE C,400000
-	AOS B
-STM2:	PUSHJ P,STM
-	JRST ZBC
-
-LARGE:	MOVE B,L1'
-	MOVE C,L2'
-	JRST STM2
-
-STM:	MOVEM B,M1'
-	MOVEM C,M2'
-	POPJ P,
-
-EQUAL:	MOVE A,M1
-	MOVE B,M2
-	PUSHJ P,SPRAB
-	JRST RESET
-
-FACTOR:	SKIPN C
-	SKIPE B
-	PUSHJ P,STM
-	MOVE D,M1
-	MOVE DV,M2
-TEST2:	JUMPN D,.+3
-	CAIG DV,3
-	JRST SPRIME
-	TRNE DV,1
-	JRST ODD
-	ASHC D,-1
-	MOVEI B,2
-PRB:	SETZM A
-	PUSHJ P,SPRAB
-	JRST TEST2
-ODD:	MOVE A,D
-	MOVE C,DV
-	IDIVI A,3
-	DIVI B,3
-	JUMPN C,NO3
-	MOVE D,A
-	MOVE DV,B
-	MOVEI B,3
-	JRST PRB
-NO3:	MOVE C,D
-	MOVE D,DV
-	MOVEI DV,5
-	HRRI INCR,4
-	JRST RETEST
-
-FOUND:	MOVE D,A
-	SETZM A
-	MOVE B,DV
-	PUSHJ P,SPRAB
-	MOVE C,Z
-	JRST RETEST
-
-SPRIME:	MOVE C,D
-	MOVE D,DV
-
-PRIME:	MOVEM C,L1
-	MOVEM D,L2
-	MOVE A,C
-	MOVE B,D
-	PUSHJ P,SPRAB
-	JRST RESET
-
-SPRAB:	PUSHJ P,SPACE
-PRAB:	MOVE C,B
-	IDIVI A,10.
-	DIVI B,10.
-	HRLM C,(P)
-	SKIPN B
-	SKIPE A
-	PUSHJ P,PRAB
-	HLRZ A,(P)
-	ADDI A,"0
-	JRST TYO
-
-SPACE:	PUSH P,A
-	MOVEI A,40
-	PUSHJ P,TYO
-	POP P,A
-	POPJ P,
-
-HUH:	MOVEI A,"?
-	PUSHJ P,TYO
-	JRST LOOP
-
-PROMPT:	PUSHJ P,CR
-	MOVEI A,"#
-	PUSHJ P,TYO
-
-CR:	MOVEI A,15
-	PUSHJ P,TYO
-	MOVEI A,12
-
-TYO:	.IOT TYOC,A
-	POPJ P,
-
-TYI:	.IOT TYIC,A
-	POPJ P,
-
-KILL:	.BREAK 16,160000
-
-CONSTANTS
-VARIABLES
-
-PDL:	BLOCK PDLL+1
-	
-PAT: 	BLOCK 100
-
-	END GO
-
\ No newline at end of file
diff --git a/src/rz/factor.27 b/src/rz/factor.27
new file mode 100644
index 00000000..e5837d5e
--- /dev/null
+++ b/src/rz/factor.27
@@ -0,0 +1,414 @@
+;Factor integers using trial division		-*-MIDAS-*-
+
+TITLE FACTOR
+
+Z=0
+A=1
+B=2
+C=3
+D=4
+E=5
+DV=5
+P=6
+
+.MLLIT==1
+KL10==1		;;KL10 RUNS SLOWER IN ACS
+
+TYIC==1
+TYOC==2
+INFOC==3
+
+PDLL==100
+
+IFE KL10,	LOC 7
+;This is the inner loop of the trial division code.
+;CD is the number being tested. DV is the candidate factor.
+;The TRC/ADDI self-modifying code means that it alternates between
+;adding 2 and 4 to DV on each iteration, so the factors it tries are
+;5, 7, 11, 13, 17, 19, 23, 25... i.e. it skips multiples of 2 and 3.
+;(See <https://oeis.org/A007310> for more about this sequence.)
+TEST:	TRC INCR,6		;Complement the 2 and 4 bits in ADDI below
+INCR:	ADDI DV,2		;Next candidate; modified by TEST/NO3
+RETEST:	MOVE Z,C
+	MOVE B,D
+	IDIV Z,DV		;Z := Z div DV; A := Z mod DV
+	DIV A,DV		;A := AB div DV; B := AB mod DV
+	CAMLE DV,A
+	 JUMPE Z,PRIME		;No more factors to try, so CD is prime
+	JUMPN B,TEST		;Not divisible by E; try the next candidate
+;That's the end of the registers; the instruction below is at 20.
+	JRST FOUND		;Found a factor (but CD may still be composite)
+
+;Entry point
+IFE KL10,	LOC 100
+GO:	MOVE P,[-PDLL,,PDL]
+	.OPEN TYIC,[.UAI,,'TTY]
+	 JRST KILL
+	.OPEN TYOC,[.UAO,,'TTY]
+	 JRST KILL
+DECIMA:	MOVEI C,10.		;Base 10 input by default
+RADSET:	MOVEM C,RADX'
+RESET:	PUSHJ P,PROMPT
+ZBC:	SETZB B,C		;BC holds current value; clear it
+
+LOOP:	PUSHJ P,TYI		;Read key and dispatch appropriately
+	ANDI A,177
+	JRST @TYIDIS(A)
+TYIDIS:	HUH	;^@
+	HUH	;^A
+	HUH	;^B
+	HUH	;^C
+	HUH	;^D
+	HUH	;^E
+	HUH	;^F
+	KILL	;^G
+	HUH	;^H
+	HUH	;^I
+	HUH	;^J
+	HUH	;^K
+	HUH	;^L
+	HUH	;^M
+	HUH	;^N
+	HUH	;^O
+	HUH	;^P
+	HUH	;^Q
+	HUH	;^R
+	HUH	;^S
+	HUH	;^T
+	HUH	;^U
+	HUH	;^V
+	HUH	;^W
+	HUH	;^X
+	HUH	;^Y
+	HUH	;^Z
+	HUH	;^[
+	HUH	;^\
+	HUH	;^]
+	HUH	;^^
+	HUH	;^_
+	STM2	;sp
+	HUH	;!
+	HUH	;"
+	HUH	;#
+	HUH	;$
+	HUH	;%
+	HUH	;&
+	HUH	;'
+	HUH	;(
+	HUH	;)
+	TIMES	;*
+	PLUS	;+
+	HUH	;,
+	MINUS	;-
+	HUH	;.
+	DIVIDE	;/
+	NUMBER	;0
+	NUMBER	;1
+	NUMBER	;2
+	NUMBER	;3
+	NUMBER	;4
+	NUMBER	;5
+	NUMBER	;6
+	NUMBER	;7
+	NUMBER	;8
+	NUMBER	;9
+	HUH	;:
+	HUH	;;
+	HUH	;<
+	EQUAL	;=
+	HUH	;>
+	INFO	;?
+
+	HUH	;@
+	HUH	;A
+	HUH	;B
+	CLIST	;C
+	DECIMA	;D
+	HUH	;E
+	FACTOR	;F
+	HUH	;G
+	QUERY	;H
+	HUH	;I
+	HUH	;J
+	HUH	;K
+	LARGE	;L
+	HUH	;M
+	LOAD	;N
+	HUH	;O
+	HUH	;P
+	HUH	;Q
+	RADSET	;R
+	HUH	;S
+	HUH	;T
+	HUH	;U
+	HUH	;V
+	HUH	;W
+	HUH	;X
+	HUH	;Y
+	HUH	;Z
+	HUH	;[
+	HUH	;\
+	HUH	;]
+	POWER	;^
+	HUH	;_
+	HUH	;`
+	HUH	;a
+	HUH	;b
+	CLIST	;c
+	DECIMAL	;d
+	HUH	;e
+	FACTOR	;f
+	HUH	;g
+	QUERY	;h
+	HUH	;i
+	HUH	;j
+	HUH	;k
+	LARGE	;l
+	HUH	;m
+	LOAD	;n
+	HUH	;o
+	HUH	;p
+	HUH	;q
+	RADSET	;r
+	HUH	;s
+	HUH	;t
+	HUH	;u
+	HUH	;v
+	HUH	;w
+	HUH	;x
+	HUH	;y
+	HUH	;z
+	HUH	;{
+	HUH	;|
+	HUH	;}
+	HUH	;~
+	RESET	;rubout
+
+NUMBER:	IMUL B,RADX		;A digit - add it to BC
+	MUL C,RADX
+	ADDI D,-"0(A)
+	TLZE D,400000
+	AOS C
+	ADD B,C
+	MOVE C,D
+	JRST LOOP
+
+INFO:	PUSHJ P,INFOPN		;Show the whole info file
+	.IOT INFOC,1
+	JUMPL A,RESET
+	CAIE A,3
+	 CAIN A,14
+	  JRST RESET
+	.IOT TYOC,1
+	JRST INFO+1
+
+INFOPN:	.CALL [	SETZ		;Open the info file
+		SIXBIT /OPEN/
+		,,[0,,INFOC]
+		,,[SIXBIT /DSK/]
+		,,[SIXBIT /FACTOR/]
+		,,[SIXBIT /ORDER/]
+		400000,,[SIXBIT /.INFO./]]
+	 JRST INFLOS
+CPOPJ:	POPJ P,
+
+INFLOS:	SUB P,[1,,1]		;Info file can't be opened
+	MOVE B,[440700,,[ASCIZ \Can't open info file\]]
+	JRST Q3
+
+QUERY:	MOVE B,[440700,,[ASCIZ/elp /]]	;Look up a key in the info file
+	PUSHJ P,OUT
+	PUSHJ P,INFOPN
+	.IOT TYIC,B		;Get a key
+	PUSHJ P,CR
+	CAIL B,"0		;Digit?
+	 CAILE B,"9
+	  JRST Q0
+	MOVE B,[440700,,[ASCIZ/	digit/]]
+	JRST Q3
+Q0:	.IOT INFOC,A		;Skip chars until LF
+	JUMPL A,Q1
+	CAIE A,12
+	 JRST Q0
+	.IOT INFOC,A		;Read first char
+	CAME A,B		;Is the key we're after?
+	 JRST Q0		;No - try next line
+	.IOT INFOC,A		;Read second char
+	JUMPL A,Q1
+	CAIE A,11		;Is it tab?
+	 JRST Q0		;No - try next line
+	JRST .+2		;Found it!
+Q2:	.IOT INFOC,A		;Copy from file to tty until LF
+	.IOT TYOC,A
+	CAIE A,12		;LF
+	 JRST Q2
+	.IOT INFOC,A		;Does next line start with tab?
+	CAIN 1,11
+	 JRST Q2+1		;Yes - print it too
+	JRST RESET
+
+CLIST:				;List all keys we know about
+	SKIPA B,[440700,,[ASCIZ 7	RD:*;+-/^NLF =QC?7]]
+Q1:				;Key not found in info file
+	MOVE B,[440700,,[ASCIZ/	IGNORED/]]
+Q3:	ILDB A,B		;Print the ASCIZ string in B and RESET
+	JUMPE A,RESET
+	.IOT TYOC,A
+	JRST Q3
+
+OUT:	ILDB A,B		;Print the ASCIZ string in B and return
+	JUMPE A,CPOPJ
+	.IOT TYOC,A
+	JRST .-3
+
+LOAD:	MOVE B,M1
+	MOVE C,M2
+	JRST LOOP
+
+POWER:	MOVEI Z,-1(C)
+	MOVE A,M2
+	SETZ B,
+	MOVE C,A
+POW1:	IMUL B,A
+	MUL C,A
+	ADD B,C
+	MOVE C,D
+	SOJG Z,POW1
+	JRST STM2
+
+DIVIDE:	MOVE A,C
+	MOVE B,M1
+	MOVE D,M2
+	IDIV B,A
+	DIV C,A
+	JRST STM2
+
+TIMES:	IMUL B,M2
+	MOVE A,C
+	IMUL A,M1
+	MUL C,M2
+	ADD B,C
+	ADD B,A
+	TLZ B,400000
+	MOVEM D,M2
+	MOVEM B,M1
+	JRST ZBC
+
+MINUS:	MOVNS C
+	ADD C,[SETZ]
+	AOS B
+	MOVNS B
+PLUS:	ADD C,M2
+	ADD B,M1
+	TLZE C,400000
+	AOS B
+STM2:	PUSHJ P,STM
+	JRST ZBC
+
+LARGE:	MOVE B,L1'
+	MOVE C,L2'
+	JRST STM2
+
+STM:	MOVEM B,M1'
+	MOVEM C,M2'
+	POPJ P,
+
+EQUAL:	MOVE A,M1
+	MOVE B,M2
+	PUSHJ P,SPRAB
+	JRST RESET
+
+FACTOR:	SKIPN C			;Factor arg in BC
+	 SKIPE B
+	  PUSHJ P,STM		;Arg isn't 0; set current value from arg
+	MOVE D,M1		;Put number being factored into DE
+	MOVE E,M2
+TEST2:	JUMPN D,.+3		;Is DE small?
+	CAIG E,3
+	 JRST SPRIME		; DE < 3 - no need to factor
+	TRNE E,1		;Is DE divisible by 2?
+	 JRST ODD		; No
+	ASHC D,-1		;Take out a factor of 2
+	MOVEI B,2
+PRB:	SETZM A
+	PUSHJ P,SPRAB		;Print factor
+	JRST TEST2		;... and factor again
+
+ODD:	MOVE A,D		;Is DE divisible by 3?
+	MOVE C,E
+	IDIVI A,3
+	DIVI B,3
+	JUMPN C,NO3		; No
+	MOVE D,A		;Take out a factor of 3
+	MOVE E,B
+	MOVEI B,3
+	JRST PRB		;Print and factor again
+
+NO3:	MOVE C,D		;Not divisible by 2 or 3: start trial division
+	MOVE D,E
+	MOVEI DV,5		;First factor to try
+	HRRI INCR,4		;Set next trial division step size
+	JRST RETEST		;... and start the inner loop
+
+FOUND:	MOVE D,A		;Trial division found a factor
+	SETZM A
+	MOVE B,DV
+	PUSHJ P,SPRAB		;Print it
+	MOVE C,Z
+	JRST RETEST		;... and keep looking (starting from same DV)
+
+SPRIME:	MOVE C,D		;DE was a trivial prime to start with
+	MOVE D,E
+PRIME:	MOVEM C,L1		;Found the largest prime factor; save it
+	MOVEM D,L2
+	MOVE A,C
+	MOVE B,D
+	PUSHJ P,SPRAB		;Print it
+	JRST RESET		;Done!
+
+SPRAB:	PUSHJ P,SPACE		;Print a space, then...
+PRAB:	MOVE C,B		;Print number in AB in decimal
+	IDIVI A,10.
+	DIVI B,10.
+	HRLM C,(P)
+	SKIPN B
+	 SKIPE A
+	  PUSHJ P,PRAB
+	HLRZ A,(P)
+	ADDI A,"0
+	JRST TYO
+
+SPACE:	PUSH P,A		;Print space
+	MOVEI A,40
+	PUSHJ P,TYO
+	POP P,A
+	POPJ P,
+
+HUH:	MOVEI A,"?		;Print ?
+	PUSHJ P,TYO
+	JRST LOOP
+
+PROMPT:	PUSHJ P,CR		;Print prompt
+	MOVEI A,"#
+	PUSHJ P,TYO
+
+CR:	MOVEI A,15		;Print CRLF - CR
+	PUSHJ P,TYO
+	MOVEI A,12		;LF
+
+TYO:	.IOT TYOC,A		;Print character in A
+	POPJ P,
+
+TYI:	.IOT TYIC,A		;Read character into A
+	POPJ P,
+
+KILL:	.BREAK 16,160000
+
+CONSTANTS
+VARIABLES
+
+PDL:	BLOCK PDLL+1
+	
+PAT: 	BLOCK 100
+
+	END GO