Homework Help: Carry and overflow flag

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1. Feb 14, 2016

kelvin56484984

1. The problem statement, all variables and given/known data
Find the carrry flag,overflow flag, set flag after these instructions
A=68H -100
B=-12+A
C=B-33H
D=C+53H
2. Relevant equations

3. The attempt at a solution
I change the value to binary
A
68H--------->1101000
100---------->1100100

1101000
- 1100100
0000100

B
12---------->1100
After 2s complement
-12---------->11110100

11110100
+ 00000100
11111000

C
33H---------->110011

11111000
- 00110011
11000101
D
53H---------->1010011

11000101
+ 01010011
101001000

So the carry flag is 1 ,
then 68H=104, 33H=51, 53H=83
{[-12+(104-100)]-51}+83
=24
Since the sign bit is 1 ,it is overflow
the overflow flag is 1
But how to find Set flag?

2. Feb 14, 2016

Hesch

You must tell what is meant by "set flag".
It depends on which programming language is used and/or which processor is used.
E.g. as for an "ARM"-processor, the "set flag" is a flag included in an assembly instruction:

ADD D0,D1,D2 means: D0 = D1+D2 without any set/reset of carry, sign, etc. ( set flag = 0 in the instruction)
whereas
ADDS D0,D1,D2 means: D0 = D1+D2 with set/reset of carry, sign, etc. ( set flag = 1 in the instruction)

So, what is meant by "set flag"?

3. Feb 15, 2016

kelvin56484984

I am not sure about the meaning but I am using assembly language for 8086.

4. Feb 15, 2016