Compilation of Chapter 4 Exercises

Exercise One: In the three-word unit starting from si, there are unsigned numbers. It is required to add these three numbers, and the result is stored in the next unit.

　　Important: Note that it is an unsigned number. During the addition, as long as CF generates a carry, an overflow will occur.

DATA SEGMENT
    BUF DW XXH,YYH,ZZH
    SUM DW ?,?
    DATA ENDS
CODE SEGMENT
    ASSUME CS:CODE,DS:DATA
START: MOV AX,DATA
    MOV DS,AX
    
    LEA SI,BUF  
    LEA DI,SUM
    MOV AX,[SI]
    ADD AX,[SI+2]
    MOV [DI],AX
    MOV AX,0
    ADC AX,O
    MOV [DI+2],AX
    MOV AX,[DI]
    MOV AX,[SI+4]
    MOV [DI],AX
    ADC [DI+2],0
    MOV AH,4CH
    INT 21H
COD ENDS
END START

Exrcise Two: Try to write a program to write 256 units starting from address offset 100H to 00H, 01H, 02H, respectively. . . . , FFH.

　　We choose LOOP cycle.

DATA SEGMENT
    ORG 100H
    BUF1 DB 256 DUP(?)
    COUNT  EQU $-BUF1
    DATA ENDS
STK SEGMENT STACK
    DB 100 DIP(?)
    STK ENDS
CODE SEGMENT 
    ASSUME CS:CODE,DS:DATA,SS:STK
    START:MOV AX,DATA
    MOV DS,AX
    MOV SI,OFFSET BUF1
    MOV CX,COUNT
    XOR AL,AL
    NEXT:MOV [SI],AL
    INC AL
    INC SI
    LOOP NEXT
    MOV AH 4CH
    INT 21H
    CODE ENDS
END START

Exercise Three: Count the 0 elements, positive numbers, and negative numbers of the elements written in the above data block, and write the same i results in the last three units of the above data block.

SEGMENT the DATA 
    ORG 100H 
    BUF1 DB 00h, 01h, 02h ,,, FFH; suppose we now define 
    COUNT EQU $ - BUF1 
    DB 3 DUP (? ) 
    The DATA ENDS 
STK SEGMENT STACK 
    DB 100 DIP (? ) 
    STK ENDS 
CODE SEGMENT 
    the ASSUME CS: CODE , DS: DATA, SS: STK 
    START: MOV AX, DATA 
    MOV DS, AX 
    MOV SI, OFFSET BUF1 
    MOV CX, COUNT 
    XOR BX, BX; used to store positive and negative 
    XOR DH, DH; used to store negative 
    NEXT2: MOV AL, [SI] 
    CMP AL, 0 
    JZ ZERO 
    JS NEGAT  
    INC BL
    JMP NEXT3   
    ZERO:INC DH
    NEGAT:INC BH
    NEXT3:INC SI
    LOOP NEXT2
    MOV [SI],DH
    INC SI
    MOV [SI],BX
    MOV AH 4CH
    INT 21H
    CODE ENDS
END START

Exercise Four: Transfer the contents of the 128 units starting from STRG1 to the units starting from STRG2.

　　Usually we generally choose the LOOP loop structure to build the program, but the MOVSB move string command can also be used for this.

DATA SEGMENT
    STRG1 DB XXH,XXH,XXH,,,,XXH
    SOUNT EQU $- STRG1
    STRG2 DB 128 DUP(?)
    DDATA ENDS
CODE SEGMENT
    ASSUME CS:CODE,DS:DATA
    START:MOV AX,DATA
    MOV DS,AX
    MOV SI,OFFSET STRG1
    LEA DI,STRG2
    MOV CX,COUNT
    CLD
    REP MOVSB
    MOV AH,4CH
    INT 21H
    CODE ENDS
END START

To be continued, to be continued ...

Compilation of Chapter 4 Exercises

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