diff --git a/bcd.h b/bcd.h
new file mode 100644
index 0000000..279a076
--- /dev/null
+++ b/bcd.h
@@ -0,0 +1,14 @@
+#ifndef BCD_H_
+#define BCD_H
+
+#include <stdint.h>
+
+uint8_t bcd_add(__idata uint8_t *v1, __idata uint8_t *v2,uint8_t len) __reentrant;
+void bcd_9cpl(__idata uint8_t *v1, uint8_t len) __reentrant;
+void bcd_shr(__idata uint8_t *v, uint8_t len, uint8_t d) __reentrant;
+void bcd_invert(__idata uint8_t *v1, uint8_t len);
+void bcd_addbyte(__idata uint8_t *v1, uint8_t len, uint8_t b) __reentrant;
+uint8_t bcd_getsig(__idata uint8_t*v, uint8_t len);
+
+#endif
+
diff --git a/bcd_9cpl.c b/bcd_9cpl.c
new file mode 100644
index 0000000..5135bc4
--- /dev/null
+++ b/bcd_9cpl.c
@@ -0,0 +1,26 @@
+
+#include "bcd.h"
+
+
+void bcd_9cpl(__idata uint8_t *v1, uint8_t len) __reentrant
+{
+	__asm
+
+        mov     a,_bp
+        add     a,#0xfd
+        mov     sp,a
+	mov	r0,dpl
+	pop	ar7
+
+	clr	c
+001$:
+	mov	a,#0x99
+	subb	a,@r0
+	mov	@r0,a
+	inc	r0
+	djnz	r7,001$
+	mov	sp,_bp
+
+	__endasm;	
+}
+
diff --git a/bcd_add.c b/bcd_add.c
new file mode 100644
index 0000000..113a994
--- /dev/null
+++ b/bcd_add.c
@@ -0,0 +1,34 @@
+#include  "mc8051fun.h"
+#include "bcd.h"
+
+#pragma disable_warning 59  // Disable "must return a value" warning
+
+uint8_t bcd_add(__idata uint8_t *v1, __idata uint8_t *v2,uint8_t len) __reentrant
+{
+	(void)v1; (void)v2; (void)len;
+	__asm
+	mov	a,_bp
+	add	a,#0xfd
+	mov	sp,a
+	pop	ar1
+	pop	ar7
+	mov	ar0,dpl
+	clr c
+001$:		
+	mov	a,@r0
+	addc	a,@r1
+	da	a
+	mov	@r0,a
+	inc	r0
+	inc	r1
+	djnz	r7,001$
+	mov	dpl,#0x00
+	jnc	$002
+	inc	dpl
+$002:
+	mov	sp,_bp
+	__endasm;
+}
+
+
+
diff --git a/bcd_addbyte.c b/bcd_addbyte.c
new file mode 100644
index 0000000..ab1dc92
--- /dev/null
+++ b/bcd_addbyte.c
@@ -0,0 +1,43 @@
+
+#include "bcd.h"
+
+#pragma disable_warning 59  // Disable "must return a value" warning
+
+void bcd_addbyte(__idata uint8_t *v1, uint8_t len, uint8_t ab) __reentrant
+{
+	(void)v1; (void)len; (void)ab;
+
+	__asm
+	mov	a,_bp
+	add	a,#0xfd
+	mov	sp,a
+
+	mov	r0,dpl
+	pop	ar7
+	pop	ACC
+	mov	r6,a
+	add	a,#0xb0	; carry will be set if a>=5
+	jc	001$
+	mov	b,#0x00
+	ajmp	004$
+001$:
+	mov	b,#0x99
+004$:
+	mov	a,@r0
+	add	a,r6
+	da	a
+	mov	@r0,a
+	sjmp	002$		
+000$:
+	inc 	r0
+	mov 	a,@r0
+	addc	a,#0x00
+	da	a
+	mov	@r0,a
+002$:
+	djnz	r7,000$
+	mov	sp,_bp
+	__endasm;
+}
+
+
diff --git a/bcd_getsig.c b/bcd_getsig.c
new file mode 100644
index 0000000..af36c15
--- /dev/null
+++ b/bcd_getsig.c
@@ -0,0 +1,10 @@
+
+#include "bcd.h"
+
+#pragma opt_code_size
+uint8_t bcd_getsig(__idata uint8_t*v, uint8_t len)
+{
+	return v[len-1]>=0x50;
+}
+
+
diff --git a/bcd_invert.c b/bcd_invert.c
new file mode 100644
index 0000000..d214f47
--- /dev/null
+++ b/bcd_invert.c
@@ -0,0 +1,11 @@
+#include "bcd.h"
+
+
+void bcd_invert(__idata uint8_t *v1, uint8_t len) 
+{
+	bcd_9cpl(v1,len);
+	bcd_addbyte(v1,len,1);
+}
+
+
+
diff --git a/bcd_shr.c b/bcd_shr.c
new file mode 100644
index 0000000..f9d9989
--- /dev/null
+++ b/bcd_shr.c
@@ -0,0 +1,38 @@
+#include "bcd.h"
+
+
+#pragma disable_warning 59  // Disable "must return a value" warning
+
+void bcd_shr(__idata uint8_t *v, uint8_t len, uint8_t d) __reentrant
+{
+	(void)v; (void)len, (void)d;
+
+	__asm
+	mov	a,_bp
+	add	a,#0xfd
+	mov	sp,a
+
+	pop	ar7	; r7 = len
+	pop	B	; 
+	mov	a,dpl
+	add	a,r7
+	mov	r0,a
+001$:
+	dec	r0
+	mov	a,@r0
+	swap	a
+	mov	r6,a
+	anl	a,#0x0f
+	orl	a,b
+	mov	@r0,a
+	mov	a,r6
+	anl	a,#0xf0
+	mov	b,a
+	djnz	r7,001$
+	
+	mov	sp,_bp
+
+	__endasm;
+}
+
+
diff --git a/mc8051fun.h b/mc8051fun.h
index d481c63..ef94b70 100644
--- a/mc8051fun.h
+++ b/mc8051fun.h
@@ -75,8 +75,6 @@ int getpin(i8051pin_T *pin);
 void setpin(i8051pin_T *pin, uint8_t val);
 uint8_t getport(int n);
 
-
-
 #define AR0 0x00
 #define AR1 0x01
 #define AR2 0x02
@@ -88,6 +86,7 @@ uint8_t getport(int n);
 
 
 
+uint8_t multest(uint8_t a, uint8_t b);
 
 
 
diff --git a/multest.c b/multest.c
new file mode 100644
index 0000000..6447540
--- /dev/null
+++ b/multest.c
@@ -0,0 +1,8 @@
+
+
+#include "mc8051fun.h"
+
+uint8_t multest(uint8_t a, uint8_t b)
+{
+	return a*b;
+}