diff --git a/libsrc/apple2/ctype.s b/libsrc/apple2/ctype.s
index 007e2cdd2..f54d50abe 100644
--- a/libsrc/apple2/ctype.s
+++ b/libsrc/apple2/ctype.s
@@ -8,16 +8,6 @@
 
 .rodata
 
-; Value that must be added to an upper case char to make it lower case
-; char (example: for ASCII, this must be $E0).
-
-
-     	.export	  	__cdiff
-
-__cdiff:
-	.byte	$E0
-
-
 ; The following 256 byte wide table specifies attributes for the isxxx type
 ; of functions. Doing it by a table means some overhead in space, but it
 ; has major advantages:
diff --git a/libsrc/atari/ctype.s b/libsrc/atari/ctype.s
index 26658679e..8dbed2700 100644
--- a/libsrc/atari/ctype.s
+++ b/libsrc/atari/ctype.s
@@ -10,16 +10,6 @@
 
 .rodata
 
-; Value that must be added to an upper case char to make it lower case
-; char (example: for ASCII, this must be $E0).
-
-
-     	.export	  	__cdiff
-
-__cdiff:
-	.byte	$E0
-
-
 ; The following 256 byte wide table specifies attributes for the isxxx type
 ; of functions. Doing it by a table means some overhead in space, but it
 ; has major advantages:
diff --git a/libsrc/cbm/ctype.s b/libsrc/cbm/ctype.s
index 4c50e09c1..5044ec9dc 100644
--- a/libsrc/cbm/ctype.s
+++ b/libsrc/cbm/ctype.s
@@ -8,16 +8,6 @@
 
 .rodata
 
-; Value that must be added to a lower case char to make it an upper case
-; char (example: for ASCII, this must be $E0).
-
-
-     	.export		__cdiff
-
-__cdiff:
-	.byte	$80
-
-
 ; The following 256 byte wide table specifies attributes for the isxxx type
 ; of functions. Doing it by a table means some overhead in space, but it
 ; has major advantages:
diff --git a/libsrc/common/stricmp.s b/libsrc/common/stricmp.s
index 62e2f847c..73cb580cb 100644
--- a/libsrc/common/stricmp.s
+++ b/libsrc/common/stricmp.s
@@ -7,27 +7,27 @@
 
  	.export		_stricmp, _strcasecmp
 	.import		popax
-	.import		__ctype, __cdiff
+	.import		__ctype
 	.importzp	ptr1, ptr2, tmp1
 
 
 _stricmp:
 _strcasecmp:
-     	sta	ptr2		; Save s2
+     	sta	ptr2	       	; Save s2
      	stx	ptr2+1
-     	jsr	popax 		; get s1
+     	jsr	popax 	       	; get s1
      	sta	ptr1
      	stx	ptr1+1
      	ldy	#0
 
-loop:  	lda	(ptr2),y	; get char from second string
+loop:  	lda	(ptr2),y       	; get char from second string
 	tax
-	lda	__ctype,x	; get character classification
-	and	#$01		; lower case char?
-	beq	L1		; jump if no
-	txa			; get character back
+	lda	__ctype,x      	; get character classification
+	and	#$01	       	; lower case char?
+	beq	L1	       	; jump if no
+	txa		       	; get character back
 	clc
-	adc	__cdiff		; make upper case char
+	adc	#<('A'-'a')     ; make upper case char
 	tax			;
 L1:	stx    	tmp1   	       	; remember upper case equivalent
 
@@ -38,7 +38,7 @@ L1:	stx    	tmp1   	       	; remember upper case equivalent
        	beq    	L2		; jump if no
 	txa	  		; get character back
 	clc
-	adc	__cdiff		; make upper case char
+       	adc    	#<('A'-'a')     ; make upper case char
 	tax
 
 L2:	cpx	tmp1		; compare characters
diff --git a/libsrc/common/strlower.s b/libsrc/common/strlower.s
index 49e906bea..858b8e181 100644
--- a/libsrc/common/strlower.s
+++ b/libsrc/common/strlower.s
@@ -9,27 +9,27 @@
 
  	.export		_strlower, _strlwr
 	.import		popax
-	.import		__ctype, __cdiff
+	.import		__ctype
 	.importzp	ptr1, ptr2
 
 _strlower:
 _strlwr:
-	sta	ptr1		; Save s (working copy)
-	stx	ptr1+1		
+	sta	ptr1	       	; Save s (working copy)
+	stx	ptr1+1
 	sta	ptr2
-	sta	ptr2+2		; save function result
+	sta	ptr2+2	       	; save function result
 	ldy	#0
 
-loop:	lda    	(ptr1),y	; get character
-	beq	L9		; jump if done
+loop:	lda    	(ptr1),y       	; get character
+	beq	L9	       	; jump if done
 	tax
-	lda	__ctype,x	; get character classification
-	and	#$02		; upper case char?
-	beq	L1		; jump if no
-	txa			; get character back into accu
+	lda	__ctype,x      	; get character classification
+	and	#$02	       	; upper case char?
+	beq	L1	       	; jump if no
+	txa		       	; get character back into accu
 	sec
-	sbc	__cdiff		; make lower case char
-	sta	(ptr1),y	; store back
+	sbc	#<('A'-'a')     ; make lower case char
+	sta	(ptr1),y       	; store back
 L1:	iny	    		; next char
 	bne	loop
 	inc	ptr1+1		; handle offset overflow
diff --git a/libsrc/common/strupper.s b/libsrc/common/strupper.s
index 80019ac9a..b330ab8c1 100644
--- a/libsrc/common/strupper.s
+++ b/libsrc/common/strupper.s
@@ -9,13 +9,13 @@
 
  	.export		_strupper, _strupr
 	.import		popax
-	.import		__ctype, __cdiff
+	.import		__ctype
 	.importzp	ptr1, ptr2
 
 _strupper:
 _strupr:
 	sta	ptr1		; Save s (working copy)
-	stx	ptr1+1		
+	stx	ptr1+1
 	sta	ptr2
 	sta	ptr2+2		; save function result
 	ldy	#0
@@ -28,7 +28,7 @@ loop:	lda    	(ptr1),y	; get character
 	beq	L1		; jump if no
 	txa			; get character back into accu
 	clc
-	adc	__cdiff		; make upper case char
+       	adc    	#<('A'-'a')     ; make upper case char
 	sta	(ptr1),y	; store back
 L1:	iny	    		; next char
 	bne	loop
diff --git a/libsrc/common/tolower.s b/libsrc/common/tolower.s
index 0c67199a3..f44aa9cad 100644
--- a/libsrc/common/tolower.s
+++ b/libsrc/common/tolower.s
@@ -5,7 +5,7 @@
 ;
 
 	.export		_tolower
-	.import		__ctype, __cdiff
+	.import		__ctype
 
 _tolower:
         cpx     #$00            ; Outside valid range?
@@ -16,6 +16,6 @@ _tolower:
 	lsr	a		; Get bit 1 (upper case char) into carry
 	tya			; Get char back into A
        	bcc    	L9		; Jump if no upper case char
-   	sbc	__cdiff	       	; Make lower case char (carry already set)
+       	sbc    	#<('A'-'a')     ; Make lower case char (carry already set)
 L9:    	rts
 
diff --git a/libsrc/common/toupper.s b/libsrc/common/toupper.s
index 5561eb7d4..adc3d4a33 100644
--- a/libsrc/common/toupper.s
+++ b/libsrc/common/toupper.s
@@ -5,7 +5,7 @@
 ;
 
 	.export		_toupper
-	.import		__ctype, __cdiff
+	.import		__ctype
 
 _toupper:
         cpx     #$00            ; Outside valid range?
@@ -16,6 +16,6 @@ _toupper:
 	tya			; Get C back into A
        	bcc    	L9		; Jump if not lower char
        	clc
-	adc	__cdiff		; make upper case char
+       	adc    	#<('A'-'a')     ; make upper case char
 L9:	rts	  		; CC are set