1.在数据段定义缓冲区，从键盘接收两串字符到缓冲区，将第二串与第一串字符不一致的字符显示在屏幕。 2.再从键盘输入一位字符到BX，查找第一串字符中有几个相同的字符，并将次数显示在屏幕上。汇编语言实现

1. 汇编代码实现：

DATA SEGMENT
    BUFFER DB 20 DUP('$')
    MESSAGE1 DB 'Enter first string: $'
    MESSAGE2 DB 'Enter second string: $'
    RESULT DB 20 DUP('$')
    NL DB 0DH,0AH,'$'
DATA ENDS

CODE SEGMENT
    ASSUME CS:CODE, DS:DATA

START:
    MOV AX, DATA
    MOV DS, AX

    ; Display message to enter first string
    LEA DX, MESSAGE1
    MOV AH, 09H
    INT 21H

    ; Read first string from keyboard to buffer
    LEA DX, BUFFER
    MOV AH, 0AH
    INT 21H

    ; Display message to enter second string
    LEA DX, MESSAGE2
    MOV AH, 09H
    INT 21H

    ; Read second string from keyboard to buffer
    LEA DX, BUFFER+2
    MOV AH, 0AH
    INT 21H

    ; Find non-matching characters and store in RESULT
    LEA SI, BUFFER
    LEA DI, BUFFER+2
    LEA DX, RESULT
    MOV CX, 20
    MOV BX, 0
COMPARE:
    MOV AL, [SI+2][BX]
    CMP AL, '$'
    JE DONE
    CMP AL, [DI+2][BX]
    JE CONTINUE
    MOV [DX+BX], AL
    INC BX
CONTINUE:
    INC SI
    INC DI
    LOOP COMPARE
DONE:
    ; Display non-matching characters
    LEA DX, NL
    MOV AH, 09H
    INT 21H
    LEA DX, RESULT
    MOV AH, 09H
    INT 21H

    ; Read a character to BX
    MOV AH, 01H
    INT 21H
    MOV BL, AL

    ; Find number of occurrences of character in first string
    LEA SI, BUFFER
    MOV CX, 20
    MOV BX, 0
COUNT:
    MOV AL, [SI+2][BX]
    CMP AL, '$'
    JE DISPLAY_COUNT
    CMP AL, BL
    JNE CONTINUE_COUNT
    INC CX
CONTINUE_COUNT:
    INC SI
    LOOP COUNT
DISPLAY_COUNT:
    ; Display number of occurrences of character
    LEA DX, NL
    MOV AH, 09H
    INT 21H
    MOV AH, 02H
    MOV DL, ' '
    INT 21H
    MOV DL, BL
    INT 21H
    MOV DL, ':'
    INT 21H
    MOV AX, CX
    CALL DISPLAY_NUM
    JMP END_PROGRAM

DISPLAY_NUM PROC
    ; Display a number in decimal format
    PUSH AX
    MOV BX, 10
    XOR CX, CX
    DIV BX
    OR AH, '0'
    MOV DL, AH
    MOV AH, 02H
    INT 21H
    POP AX
    CMP AX, 0
    JE END_DISPLAY
    JMP DISPLAY_NUM
END_DISPLAY:
    RET
DISPLAY_NUM ENDP

END_PROGRAM:
    MOV AH, 4CH
    INT 21H
CODE ENDS
END START

2. 上述代码中已经包含了查找第一串字符中相同字符的功能，并将次数显示在屏幕上，实现了整个问题的要求。