57 lines
1.9 KiB
NASM
Executable File
57 lines
1.9 KiB
NASM
Executable File
DATA SEGMENT
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CHAR DB 'A'
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HINT1 DB 'Please enter a string: $'
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HINT2 DB 10, 27H, 'A', 27H, ' occured time: $'
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TIMES DB 0
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MAXLEN DB 100
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LEN DB 0
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TABLE DB 100 DUP (0)
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DATA ENDS
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CODE SEGMENT
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ASSUME CS:CODE, DS:DATA
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START:
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MOV AX, DATA
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MOV DS, AX
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MOV DX, OFFSET HINT1 ; 将HINT1的偏移地址赋给DX准备输出
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MOV AH, 9 ; 输出
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INT 21H
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LEA DX, MAXLEN ; 0AH功能会获取DS:[DX](已定义为MAXLEN)作为输入缓冲区最大容量
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MOV AH, 0AH ; 调用0AH功能，将输入的字符串长度存入DS:[DX+1](已定义为LEN)
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INT 21H ; 将字符串存入从DS:DX+2开始的空间(已定义为TABLE)
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CALL CNT ; 统计字符“A”的数量，结果在TIMES中
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MOV DX, OFFSET HINT2 ; 将HINT2的偏移地址赋给DX准备输出
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MOV AH, 9 ; 输出
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INT 21H
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MOV AL, TIMES
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ADD AL, '0' ; TIMES += '0' (将数字信息转换成字符)
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MOV DL, AL
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MOV AH, 02H ; 显示单个字符
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INT 21H
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MOV AH,4CH
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INT 21H
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CNT PROC NEAR
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MOV CX, 0
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MOV CL, LEN
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MOV SI, -1 ; SI是遍历TABLE的下标
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MOV AL, CHAR ; 要比较的字符移到AL中(CMP不能比较两个内存单元)
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LP:
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INC SI
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CMP AL, TABLE[SI]
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JNE BACK ; 不相等则跳过INC TIMES，重新循环
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INC TIMES
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BACK:
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LOOP LP ; LOOP先将CX -= 1，然后判断是否为0，为0就退出循环
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RET
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CNT ENDP
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CODE ENDS
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END START
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