MHB Multiplication with binary unsigned numbers

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The discussion revolves around the multiplication of binary unsigned numbers and the interpretation of negative results in two's complement. A user questions why multiplying two negative numbers yields a positive result that doesn't match expected values, specifically referencing the binary multiplication of 1111010 and 1001. Clarification is provided that the leftmost bit's significance depends on the number of bits used, and that leading zeros must be considered in determining the sign of the number. The importance of knowing the bit count is emphasized to correctly interpret the results in two's complement. Understanding these principles is crucial for accurate binary arithmetic.
shamieh
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1111010 x 1001 is a negative * a negative so I should get a positive right?

which I got 0001001010.

BUT, if it's -122 x -9 = 1098. How come I get a positive number that doesn't equal 1098. Aren't you supposed to disregard the most left bit if it's more numbers than your original like wouldn't i disregard the 1 carry in 10001001010, because if I included it in the answer wouldn't that make it -122 * -9 which = -1098. And how is that possible.
 
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shamieh said:
1111010 x 1001 is a negative * a negative
Why are you saying that? First, are you talking about 2's complement? Second, what number of bits do you have? Only when you know the number of bits, you can say which numbers are negative in 2's complement: the leftmost bit must be 1. But the leftmost bit here means that you have to use all bits, even if this means leading zeros. For example, if you have 8 bits, then 1001 is 00001001, the leading bit is 0 and the number is positive.
 

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