Question

THIS IS A MICROPROCESSOR ASSEMBLY LANGUAGUE. I USE TEXTPAD 7 TO TYPE CODE AND DEBUG CODE BY DOSBOX

1. Factorial(N) = n*(n-1)*(n-2)*...*2*1

   • (a) Write a procedure to calculate F(N). Pass the offsets of N and F. The procedure returns nothing. Create a stackframe before the procedure call, and destroy it after the call.

   • (b) Write a macro to calculate F(N). Pass the offsets of N and F to the macro

Answer 1

Hi,

The assembly language code to calculate factorial of a number is shown below.

.model small
.data
   x dw 5 -- Here we are calculating the factorial of 5. dw stands for define word.
.code
   mov ax,@data -
   mov ds,ax - we cannot move data into the ds directly. we have to use ax register to move data to the ds(data segment)

   mov cx,x - initializing counter register(cx) to the value x i.e., 5
   mov ax,x -initializing ax to the value x i.e., 5
   call fact - calling fact funtion

fact:
l: dec x - decrementing the x value by 1.
mul x - multiplies ax with x and stores the result in ax.
dec cx - decrementing counter register(cx) by1 .
jnz l - we have to repeat this procedure till counter register(cx) becomes 0. When it is '0' it need to exit the loop.
ret - the ax value will be return.
  
   mov ah,4ch
   int 21h
end
  

b)macro to calculate factorial of a number:

FACTORIAL MACRO F ----DEFINING FACTORIAL MACRO
L: ----LABEL TO LOOP BACK TO THE DESIRED LOCATION
MUL F ----MULTIPLY THE NUMBER IN THE F REGISTER
DEC F --- DECREMENT THE NUMBER
JNZ L --- JUMP IF NOT ZERO TO L BACK
ENDM ---END OF MACRO

DATA SEGMENT ---INITIALIZE DATA SEGMENT
X DW 06H ---INITIALIZE X ANY DATA
RESULT DW ? ---INITIALIZE RESULT
DATA ENDS ---END OF DATA SEGMENT

CODE SEGMENT ---INITIALIZE CODE SEGMENT
START: ---START THE CODE
ASSUME CS:CODE , DS:DATA --ASSUMPTION OF CODE AND DATA
MOV AX,DATA ---MOV DATA INTO ACCUMULATOR AX
MOV DS,AX ---MOV DATA FROM ACCUMULATOR INTO DATA SEGMENT REGISTER
MOV CX,X ---MOV X INTO THE CODE SEGMENT CX REGISTER WE MOVE THE NUMBER INTO CS REGISTER BECAUSE CS REGISTER ACT AS COUNT
MOV AX,0001H ---MOV CONSTANT 0001H INTO AX
FACTORIAL X ---CALL THE MACRO FUNCTION BY SPECIFYING NAME OF PARAMETERS (OBJECT) TO PASS
MOV RESULT,AX ----MOVE THE RESULT FROM AX INTO RESULT VARIABLE
MOV AH,4CH -----;END OF THE CODE
INT 21H ----- ;END OF THE CODE
CODE ENDS ----END OF CODE SEGMENT
END START ----END OF START

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