;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; UCASE
;; This function converts a string to
;; all-uppercase letters.
;;
;;   DS:SI <- pointer to $-terminated string
;;   ES = DS
;;
;; Destroyed: AL,SI,DI,flags

UCASE:
	MOV	DI,SI
	CLD
UCASE_Loop:
	LODSB
	CMP	AL,"$"
	JE	UCASE_Exit
	CMP	AL,"a"
	JB	UCASE_Loop
	CMP	AL,"z"
	JA	UCASE_Loop
	AND	AL,11011111b
	STOSB
	JMP	UCASE_Loop
UCASE_Exit:
	RET