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Write a program in assembly language such that: a. Two binary numbers are saved in two separate memory locations. b. As the numbers are added, an overflow will occur. c. As the numbers are added, no overflow occurs. Check whether an overflow occurred or not from the status register.
Expert Answer
(a)
MVI A, 2H ;Copy value 2H in register A
MVI B, 4H ;Copy value 4H in register B
DATA SEGMENT
NUM1 DB 8H
NUM2 DB 8H
SUM DB ?
ENDS
CODE SEGMENT
ASSUME DS:DATA CS:CODE
START:
MOV AX,DATA
MOV DS,AX
MOV AL,NUM1
ADD AL,NUM2
MOV SUM,AL
INT 21H
ENDS
END START
(b)
If the sum of two numbers with the sign bits off yields a result number with the sign bit on, the "overflow" flag is turned on. 0100 + 0100 = 1000 (overflow flag is turned on) If the sum of two numbers with the sign bits on yields a result number with the sign bit off, the "overflow" flag is turned on. 1000 + 1000 = 0000 (overflow flag is turned on)
(c)
Otherwise, the overflow flag is turned off. * 0100 + 0001 = 0101 (overflow flag is turned off) * 0110 + 1001 = 1111 (overflow flag is turned off) * 1000 + 0001 = 1001 (overflow flag is turned off) * 1100 + 1100 = 1000 (overflow flag is turned off) We only need to look at the sign bits (leftmost) of the three numbers to decide if the overflow flag is turned on or off
