汇编程序

从键盘输入一个字符串,先把它原样显示一遍;然后将其中的小写字母转换为大写显示,再将其中的大写字母转换为小写显示,最后将其中的大小写字母互换显示.显示字符串的功能调用采用宏,大写转换,小写转换和大小写互换写成子程序.
要求:
(1). 编写一个完整的源程序完成题目的要求.
(2). 把子程序单独写在一个文件中,用源程序包含的方法完成题目要求.
(3). 把子程序单独汇编,用目标文件链接的方法完成题目要求.
(4). 把子程序加入到一个子程序库中,用子程序库调入的方法完成题目要求.

PUBLIC  UPPERTOLOWER
        DATA  SEGMENT   COMMON
    SOURESTR  DB        20
              DB        0
              DB        20 DUP('$')
        ;STR1  DB        '$'
    UPPERSTR  DB        20 DUP('$')
    LOWERSTR  DB        20 DUP('$')
   CHANGESTR  DB        20 DUP('$')
        DATA  ENDS
        CODE  SEGMENT
            UPPERTOLOWER  PROC      FAR
              ASSUME    CS:CODE,DS:DATA
              MOV       AX,DATA
              MOV       DS,AX
              PUSH      AX
              PUSH      CX
              PUSH      SI
              PUSH      BX
              MOV       SI,OFFSET SOURESTR +2
              MOV       BX,OFFSET LOWERSTR
              MOV       CX,20
      NEXT1:  MOV       AL,[SI]
              CMP       AL,'A'
              JB        RESTR2
              CMP       AL,'Z'
              JA        RESTR2
              OR        AL, 00100000B
              MOV       [BX],AL
              JMP       EXIT1
     RESTR2:
              MOV       [BX],AL
      EXIT1:
              INC       SI
              INC       BX
              LOOP      NEXT1
              POP       BX
              POP       SI
              POP       CX
              POP       AX
              RET
            UPPERTOLOWER  ENDP
        CODE  ENDS
              END
小写字母转换为大写:
      PUBLIC  LOWERTOUPPER
        DATA  SEGMENT   COMMON
    SOURESTR  DB        20
              DB        0
              DB        20 DUP('$')
      ;  STR1  DB        '$'
    UPPERSTR  DB        20 DUP('$')
    LOWERSTR  DB        20 DUP('$')
   CHANGESTR  DB        20 DUP('$')
        DATA  ENDS
        CODE  SEGMENT
            LOWERTOUPPER  PROC      FAR
              ASSUME    CS:CODE,DS:DATA
              MOV       AX,DATA
              MOV       DS,AX
              PUSH      AX
              PUSH      CX
              PUSH      SI
              PUSH      BX
              MOV       SI,OFFSET SOURESTR+2
              MOV       BX,OFFSET UPPERSTR
              MOV       CX,20
      NEXT2:  MOV       AL,[SI]
              CMP       AL,'a'
              JB        RESTR1
              CMP       AL,'z'
              JA        RESTR1
              AND       AL, 11011111B
              MOV       [BX],AL
              JMP       EXIT2
     RESTR1:
              MOV       [BX],AL
      EXIT2:
              INC       SI
              INC       BX
              LOOP      NEXT2
              POP       BX
              POP       SI
              POP       CX
              POP       AX
              RET
            LOWERTOUPPER  ENDP
        CODE  ENDS
              END
小写转换和大小写互换:
      PUBLIC  CHANGE
        DATA  SEGMENT   COMMON
    SOURESTR  DB        20
              DB        0
              DB        20 DUP('$')
      ;  STR1  DB        '$'
    UPPERSTR  DB        20 DUP('$')
    LOWERSTR  DB        20 DUP('$')
   CHANGESTR  DB        20 DUP('$')
        DATA  ENDS
        CODE  SEGMENT
      CHANGE  PROC      FAR
              ASSUME    CS:CODE,DS:DATA
              MOV       AX,DATA
              MOV       DS,AX
              PUSH      AX
              PUSH      CX
              PUSH      SI
              PUSH      BX
              MOV       SI,OFFSET SOURESTR+2
              MOV       BX,OFFSET CHANGESTR
              MOV       CX,20
      NEXT3:  MOV       AL,[SI]
              CMP       AL ,'A'
              JB        RESTR
              CMP       AL,'Z'
              JB        LOWER2
              CMP       AL,'a'
              JB        RESTR
              CMP       AL,'z'
              JA        RESTR
              AND       AL, 11011111B
              MOV       [BX],AL
              JMP       EXIT3
     LOWER2:
              OR        AL, 00100000B
              MOV       [BX] ,AL
              JMP       EXIT3
      RESTR:
              MOV       [BX],AL
      EXIT3:
              INC       SI
              INC       BX
              LOOP      NEXT3
              POP       BX
              POP       SI
              POP       CX
              POP       AX
              RET
      CHANGE  ENDP
        CODE  ENDS
              END
主程序:
       EXTRN  CHANGE:FAR
       EXTRN  UPPERTOLOWER:FAR
       EXTRN  LOWERTOUPPER:FAR
     DISPMSG  MACRO     MESSAGE     ;显示message字符串
              MOV       DX,OFFSET MESSAGE
              MOV       AH,9
              INT       21H
              MOV       DL,0AH
              MOV       AH,02H
              INT       21H
              MOV       DL,0DH
              MOV       AH,02H
              INT       21H
              ENDM
        DATA  SEGMENT   COMMON
    SOURESTR  DB        20
              DB        0
              DB        20 DUP('$')
       ; STR1  DB        '$'
    UPPERSTR  DB        20 DUP('$')
    LOWERSTR  DB        20 DUP('$')
   CHANGESTR  DB        20 DUP('$')
        STR1  DB        'LOWER TO UPPER LETTER:$'
        STR2  DB        'UPPER TO LOWER LETTER:$'
        STR3  DB        'CHANGE THE LOWER AND THE UPPER LETTER:$'
        DATA  ENDS
        CODE  SEGMENT
        MAIN  PROC      FAR
              ASSUME    CS:CODE,DS:DATA
      START:
              MOV       AX,DATA
              MOV       DS,AX
              MOV       DX,OFFSET SOURESTR
              MOV       AH,0AH
              INT       21H
              MOV       DL,0AH
              MOV       AH,02H
              INT       21H
              MOV       DL,0DH
              MOV       AH,02H
              INT       21H
              ;LEA       DX,SOURESTR+2
              ;MOV       AH,09H
             ; INT       21H
              DISPMSG   SOURESTR+2
              CALL      FAR PTR  UPPERTOLOWER
              DISPMSG   STR2
              DISPMSG   LOWERSTR
              CALL      FAR PTR LOWERTOUPPER
              DISPMSG   STR1
              DISPMSG   UPPERSTR
              CALL      FAR PTR CHANGE
             ; MOV       DX,OFFSET CHANGESTR
              ;MOV       AH,09H
              ;INT       21H
              DISPMSG   STR3
              DISPMSG   CHANGESTR
              MOV       AX,4C00H
              INT       21H
        MAIN  ENDP
        CODE  ENDS
              END       START