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Assembly questions

Posted on 2000-03-27
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Last Modified: 2010-04-02
QUESTION 1:
I have this program that calculates the factorial of numbers between 0 and 5 including them. The problem I have is that i want to write the final result to the variable called Fact and then print the resukt on screen, but it ain't working. Getting a warning.Here is what i Have:

;factorial of numbers

DATA SEGMENT
MES1 DB "ENTER NUMBER (0<=N<=5): $"
MES2 DB "THE RESULT IS: $"
FACT DB ?
DATA ENDS

STACK SEGMENT
DW 100 DUP(?)
STACK ENDS

CODE SEGMENT
ASSUME DS:DATA,CS:CODE

START:

MOV AX,DATA
MOV DS,AX

MOV AH,02H     ;making a return
MOV DL,0DH
INT 21H
MOV DL,0AH
INT 21H

MOV AH,09     ;prompt for first number
MOV DX,OFFSET MES1
INT 21H

MOV AH,01 ;input first number
INT 21H
MOV BL,AL

MOV AH,02H ;making a return
MOV DL,0DH
INT 21H
MOV DL,0AH
INT 21H

MOV BH,00H
MOV AX, BX
AAS ;adjust number to be decremented
MOV BX,AX

IF00: CMP BX,00
JNE ONE       ;routine for a 0 entry
THEN00: INC BX
MOV AX,1

ONE:
IF01: CMP BX,01  ;check if number is 1
JNE NOT_ONE    
THEN01: JMP CALC  ;jump to CALC
NOT_ONE: DEC BX

CALC: MUL BX
DEC BX
JNZ CALC

MOV DI,AX
MOV FACT,DI
AAM    ;adjust after multiplication

MOV CX,AX

MOV AH,00H
AAM
MOV BX,AX  ;BL contains the last digit of the result

MOV AL,CH
MOV AH,00H
AAM
MOV CX,AX  ;CX contains the first two digits of the resul

ADD CX, 3030H
ADD BX, 3030H ;adjust ASCII

MOV AH,09 ;output mess2
MOV DX,OFFSET MES2
INT 21H

MOV AH,02
MOV DL,CH
INT 21H
         ;print most significant digit
MOV AH,02
MOV DL,CL
INT 21H
         ;print middle digit
MOV AH,02
MOV DL,BL
INT 21H
           ;print last digit
MOV AH,4CH ;exit dos
INT 21H

CODE ENDS
END START







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Question by:milalik
9 Comments
 

Author Comment

by:milalik
Comment Utility
Question 2:

can anyone give me an example of how i deal with 16 bit signed numbers in Assembly. They include negative numbers. Please provide an example.Trying to do an array with ten signed numbers.
Thanx




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Author Comment

by:milalik
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Adjusted points from 50 to 70
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LVL 10

Expert Comment

by:RONSLOW
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That is funny looking C++ :-)
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LVL 5

Expert Comment

by:Wyn
Comment Utility
->can anyone give me an example of how i deal with 16 bit signed numbers in Assembly. They include negative numbers.
=========================
declare it and use a register as index.
K               word    ?
WArray          sword    0, -1, 2,- 3

mov K 1
;AX := WordAry[K]
mov     bx, K          
add     bx, bx
;Index*2 since this is a word array.
mov     ax, WordAry[bx]


Regards
W.Yinan
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Author Comment

by:milalik
Comment Utility
For the second question, what if i want to enter it from the keyboard?
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LVL 22

Accepted Solution

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nietod earned 75 total points
Comment Utility
The problem is that you can't treat the bytes of a multi-byte number seperately like that.  You are trying to convert a 2 byte binary number to a 4 character ASCII number by converting the low byte to two digits and the high byte to two digits.  That can't work.  Consider 0100h which is 256 decimal.  You are going to get '00' from the the low byte and '01" from the high byte or "0100" which is the correct result--in hex.

you will need to divide the number by 1000 and look at the remainder, that is the 1st digt.  subtract off 1000* this digit and then divide by 100 to get the 2nd digit....
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Author Comment

by:milalik
Comment Utility
Is this for the first question or the second one?

Please correct the problem in the first question and provide and exmple that deals with 16 bits signed numbers if you can.

Thanx
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Author Comment

by:milalik
Comment Utility
Adjusted points from 70 to 75
0
 
LVL 22

Expert Comment

by:nietod
Comment Utility
for the first question.  I'm not sure what the 2nd question even means.  but you are supposed to ask only one question per EE question (unless they are VERY closely related).  This is stated within the EE rules.  

I've outlined how you can perform the conversion.  Do you have any questions about it?
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