# IEEE754

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Hi everyone,

It's been forever since I've logged in, how is everyone?

Anyway, I'm taking a computer architecture class and our professor does not speak English very well at all, and he does not know how to teach the material. I'm having trouble with presenting numbers as single-precision floating point numbers. I can do it ok when it's a positive number, but when it's a negative I have trouble. I'm trying to represent -4A0D.8 in this format.

This is what I have:
4A0D.8 = 0100101000001101.1000
-4A0D.8 = 1011010111110010.0111 + 1 (using two's complement) = 1011010111110011.0111

So:
the sign is 1 because it is a negative
the exponent is 15, or 1111, which gets converted to Excess 127 (0111111 + 00001111 = 10001110)
so it becomes 1.0110101111100110111, with 1 as the sign and 10001110 as the exponent.

1 10001110 01101011111001101110...0 (last section has 23 digits)

Is this correct? Can anyone help me please?

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IEEE754 does not use two's complement to store negative values, it uses a sign-magnitude format. The magnitude is the absolute value of the number, and a sign bit determines whether it is a positive or a negative value. So except for the sign bit, the bit patters are identical for positive and corresponding negative values.

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Thanks. So... it would be -1.001010000011011*2^1110...

1 10001101 0010100000110110...0?

Is that closer?

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Yes, that is more like it, although IEEE754 also does not store the leading 1-bit of the normalized value. This saves one bit that is used to increase the number of bits in the mantissa.

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Ok. Thanks for your help with this.

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Anyway, I'm taking a computer architecture class and our professor does not speak English very well at all, and he does not know how to teach the material.

I've heard complaints of this type often in American universities, and I just don't understand it. This is just unacceptable and you should complain to your university about it They owe you a good education.

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