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CONTRIBUTIONS/cpm-handbook/cpmsrc/FIG5-3.ASM

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+; Figure 5-3
+;
+;	Useful subroutines using the Write Console Byte
+;	BDOS Function.
+;
+;	MSGOUT
+;	Output null-byte terminated message
+;
+;	Calling sequence
+;
+;	MESSAGE:	DB	'Message',0
+;		:
+;		LXI	H,MESSAGE
+;		CALL	MSGOUT
+;
+;	Exit Parameters
+;		HL -> Null byte terminator
+;
+B$CONOUT	EQU	2	;Write console byte
+BDOS		EQU	5	;BDOS Entry Point
+;
+MSGOUT:
+	MOV	A,M	;Get next byte for output
+	ORA	A
+	RZ		;Return when null-byte
+	INX	H	;Update message pointer
+	PUSH	H	;Save updated pointer
+	MOV	E,A	;Ready for BDOS
+	MVI	C,B$CONOUT	;Function code
+	CALL	BDOS
+	POP	H	;Recover message pointer
+	JMP	MSGOUT	;Go back for next character
+
+