I am looking at some examples in the 1750A format webpage and some of the examples do not really make sense. I have included the 1750A format specification at the bottom of this post in case anyone isn’t familiar with it.
Take this example from Table 3 of the 1750A format webpage:
.625x2^4 = 5000 00 04
In binary 5000 00 04 is 0101 0000 0000 0000 0000 0000 0000 0100
If you convert this to decimal, it does not equal 10, which is .625×2^4. Maybe I am converting it incorrectly.
Take the mantissa, 101 0000 0000 0000 0000 0000 and subtract 1 giving 100 1111 1111 1111 1111 1111. Then flip the bits, giving 011 0000 0000 0000 0000 0000. Move the decimal 4 places (since our exponent, 0100 is 4), giving us 0110.0000 0000 0000 0000 000. This equals 6.0, which is not .625×2^4.
I believe the actual value, should be 0011 0000 0000 0000 0000 0000 0000 01000 or 30000004 in hex.
Can anyone else confirm my suspicions that this value is labeled incorrectly in Table 3 of the 1750A format page above?
Thank you
As explained previously, the sign+mantissa is interpreted as a 2’s-complement value between -1 and +1.
In your case, it’s 0.101000000… (base-2). Which is 1/2 + 1/8 = 0.625 (base-10).