diff --git a/common/common.asm b/common/common.asm
index 1600911..8bd4165 100644
--- a/common/common.asm
+++ b/common/common.asm
@@ -241,7 +241,15 @@ _DCR	.(		; DCR r			6r		Rr <- Rr - 1.0	- decrement register
 	BNE _ADDI0X
 .)
 
-_TST	.(		; TST r			7r		F <- Rr <=> 0.0	- test register
+_NEG	.(		; NEG r			7r		Rr <- -Rr	- negate register
+	RTS
+.)
+
+_INV	.(		; INV r			8r		Rr <- 1.0 / Rr	- multiplicative inverse of register
+	RTS
+.)
+
+_TST	.(		; TST r			9r		F <- Rr <=> 0.0	- test register
 	LDA _F
 	AND #_MSK_T	; clear TST bits
 	STA _F
@@ -261,14 +269,6 @@ _3	ORA _F
 	RTS
 .)
 
-_DEC	.(		; DEC r			8r		Rr <- dec(Rr)	- convert Rr from hex aabbccdd to decimal ######.###
-	RTS
-.)
-
-_HEX	.(		; HEX r			9r		Rr <- hex(Rr)	- convert Rr from decimal ######.### to hex aabbccdd
-	RTS
-.)
-
 _GETPQ	.(		; sets X as p register and Y as q register, advances PC
 	LDY #0
 	LDA (_PC),Y	; get source registers
@@ -936,8 +936,8 @@ _END_CMN_CD
 
 FN_0X	.WORD _ESC-1, _RTN-1, _BRS-1, _BRA-1, _BRE-1, _BRG-1, _BRL-1, _BRZ-1,
 	.WORD _BRP-1, _BRN-1, _BRO-1, _BRU-1, _CPR-1, _LDI-1, _SVI-1, _CMR-1
-FN_XR	.WORD _SET-1, _POP-1, _PSH-1, _EXC-1, _INR-1, _DCR-1, _TST-1,
-	.WORD _DEC-1, _HEX-1, _ADD-1, _SUB-1, _MUL-1, _DIV-1, _MOD-1
+FN_XR	.WORD _SET-1, _POP-1, _PSH-1, _EXC-1, _INR-1, _DCR-1, _NEG-1,
+	.WORD _INV-1, _TST-1, _ADD-1, _SUB-1, _MUL-1, _DIV-1, _MOD-1
 
 _END_CMN_DT
 
diff --git a/common/common.h b/common/common.h
index 9330ebd..0db4f6e 100644
--- a/common/common.h
+++ b/common/common.h
@@ -6,10 +6,11 @@
 ; to be able to recognize an overflow/underflow situation, rescale the arguments, and repeat the
 ; calculation.
 
-; Largest value:              $3fffffff or +1048575.999(5)
-; Smallest value:             $c0000000 or -1048576.000(0)
-; Largest value for DEC/HEX:  $3d08ffff or  +999999.999
-; Smallest value for DEC/HEX: $c2f70001 or  -999999.999
+;  Largest value: $3fffffff or +1048575.999(5)
+;       Plus one: $00000400
+;           Zero: $00000000
+;      Minus one: $fffffc00		
+; Smallest value: $c0000000 or -1048576.000(0)
 
 ; Instructions
 
@@ -19,9 +20,9 @@
 ; EXC r			4r		Rr <-> RS	- exchange Rr with stack
 ; INR r			5r		Rr <- Rr + 1.0	- increment register
 ; DCR r			6r		Rr <- Rr - 1.0	- decrement register
-; TST r			7r		F <- Rr <=> 0.0	- test register
-; DEC r			8r		Rr <- dec(Rr)	- convert Rr from hex aabbccdd to decimal ######.###
-; HEX r			9r		Rr <- hex(Rr)	- convert Rr from decimal ######.### to hex aabbccdd
+; NEG r			7r		Rr <- -Rr	- negate register
+; INV r			8r		Rr <- 1.0 / Rr	- multiplicative inverse of register
+; TST r			9r		F <- Rr <=> 0.0	- test register
 ; ADD r pq		ar pq		Rr <- Rp + Rq	- addition
 ; SUB r pq		br pq		Rr <- Rp - Rq	- subtraction
 ; MUL r pq		cr pq		Rr <- Rp * Rq	- multiplication
@@ -124,9 +125,9 @@ _POP_C	= $30
 _EXC_C	= $40
 _INR_C	= $50
 _DCR_C	= $60
-_TST_C	= $70
-_DEC_C	= $80
-_HEX_C	= $90
+_NEG_C	= $70
+_INV_C	= $80
+_TST_C	= $90
 _ADD_C	= $a0
 _SUB_C	= $b0
 _MUL_C	= $c0
diff --git a/common/macros.h b/common/macros.h
index aef0d60..0dd1a30 100644
--- a/common/macros.h
+++ b/common/macros.h
@@ -62,9 +62,9 @@
 #define EXC(r)		.BYTE _EXC_C + r
 #define INR(r)		.BYTE _INR_C + r
 #define DCR(r)		.BYTE _DCR_C + r
+#define NEG(r)		.BYTE _NEG_C + r
+#define INV(r)		.BYTE _INV_C + r
 #define TST(r)		.BYTE _TST_C + r
-#define DEC(r)		.BYTE _DEC_C + r
-#define HEX(r)		.BYTE _HEX_C + r
 #define ADD(r, p, q)	.BYTE _ADD_C + r, p * 16 + q
 #define SUB(r, p, q)	.BYTE _SUB_C + r, p * 16 + q
 #define MUL(r, p, q)	.BYTE _MUL_C + r, p * 16 + q
diff --git a/common/page6.src b/common/page6.src
index 9b2a338..e767536 100644
--- a/common/page6.src
+++ b/common/page6.src
@@ -14,15 +14,14 @@ HDR(DEMO)
 	BRK
 
 BGN(FACTORIAL)
-	SET(R1, $10.4456)
+	SET(R1, 10.4456)
 	SET(R2, 1)
-	HEX(R1)
 	MOD(R3, R1, R2)
 	SUB(R1, R1, R3)
 _1	TST(R1)
 	BRZ(_2)
 	MUL(R2, R2, R1)
-	DEC(R1)
+	DCR(R1)
 	BRA(_1)
 _2	EXT(S0)
 	RTN