Consider the arithmetic operations with sign magnitude representation. Assume we want to calculate BA + 13 and the base is Hex. What is the result?!
We know that that the MSB bit is the sign bit. So we are performing
1101 1010
+ 0001 0011
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That means the first number is negative and the second one is positive. How do we determine the sign? Other bits are pretty simple:
X100 0111