汇编进行大小写转换

代码

ASSUME CS:CODESG,DS:DATASG,SS:STACKSG
DATASG SEGMENT
    STR DB 'hello WORLD',00AH,'$'
DATASG ENDS

STACKSG SEGMENT
    DB 010H DUP (0FFH)
STACKSG ENDS

CODESG SEGMENT
    INIT:
        MOV     AX,DATASG
        MOV     DS,AX
        MOV     AX,STACKSG
        MOV     SS,AX
        MOV     SP,010H
        JMP START
    START:
        ;转小写
        MOV BX,020H
        MOV SI,00000H
        MOV CX,00BH ;11
        S0:
            MOV AL,STR[SI]
            OR  AL,BL
            MOV STR[SI],AL
            INC SI
        LOOP S0
        LEA DX,STR[0]
        MOV AX,00900H
        INT 21H
        ;转大写
        NOT BX
        MOV SI,00000H
        MOV CX,00BH 
        S1:
            MOV AL,STR[SI]
            AND AL,BL
            MOV STR[SI],AL
            INC SI
        LOOP S1
        LEA DX,STR[0]
        MOV AX,00900H
        INT 21H
        ;退出
        MOV AX,04C00H
        INT 21H
CODESG ENDS
END INIT

解释

ASCII

由此可货上020H转换成小写
与上020H转换成大写