Added a division subroutine

src/GRAPHTST.ASM

@@ -6,6 +6,7 @@
 MsgStr: DB 'Hello, world.',13,10,0
 ClsStr: DB 27,'[2J',0
 HmeStr: DB 27,'[H',0
+CurPos: DS 11
 Stack:  DW 0             ; place to save the old stack
 SBOT:   DS 32            ; reserve a local stack
 ; Constants
@@ -34,6 +35,37 @@ CLS:    LXI H, ClsStr    ; Load the escape sequence
 HOME:   LXI H, HmeStr    ; Load the escape sequence
 		CALL PRINTF      ; print the sequence
 		RET
+; DIV: Divides a 16 bit number by an 8bit number using rotation
+;      The dividend is stored in BC and the divisor in D
+DIV:    MVI E,9          ; bit counter
+		MOV A,B          ; move the MSB to the accumulator
+DIV0:   MOV B,A          ; store the current MSB in B
+		MOV A,C          ; rotate carry into C register
+		                 ; rotate next most significant bit
+						 ; to carry.
+		MOV C,A
+		DCR E            ; decrease E
+		JZ DIV2          ; if E==0, cleanup
+		MOV A,B          ; rotate most significat but to 
+		RAL              ; high order quotient
+		JNC DIV1         ; if no carry, check, if divisior is valid
+		SUB D            ; substract divisor
+		JMP DIV0         ; and loop
+DIV1:   SUB D            ; substract divisor. if less than high-order
+        JNC DIV0         ; quotient, loop
+		ADD D            ; otherwise, add it back
+		JMP DIV0         ; and then loop
+DIV2:   RAL              ; rotate left
+        MOV E,A          ; store A to E
+		MVI A,0FFH       ; complement the quotient
+		XRA C            ; 
+		MOV C,A          ; store the complemtn in C
+		MOV A,E          ; 
+		RAR              ; rotate the A register.
+		RET              ; return to the caller
+; SETCUR: Places the cursor anywhere on the screen. 
+;         Coordinates are stored in a memory location that
+;         is referred to by HL
 ; Start of the main code block
 START:  LXI H, 0         ; blank out HL
 		DAD SP           ; HL = SP