From: John (john_at_ucc.gu.uwa.edu.au)
Date: 2002-10-04 17:42:07
firstname.lastname@example.org writes: >Questions: >- It says the first bit is used for the sign. So what is the function of $66 >??? There are two floating point formats used in the C64. "packed' has the sign in the first bit, and occupies five(?) bytes. 'unpacked' has the sign in a separate byte. It's easier for processing, but takes more memory. Packed is used for variables, unpacked in the FACs. >- If I understand well the other 31 bits hold the data representing the >number right of the decimal point. But in what format? It's been a long, long time. There should be one sign bit, some number of exponent bits (probably stored in excess-N format), then the rest is the fraction. value = sign * 2^(exp-N) * 1.fraction There are a few constants in the ROMs, such as 1.0, 10.0, PI, and a few others. You should be able to work out how many bits the exponent and fraction take, and what the exponent excess is. John Message was sent through the cbm-hackers mailing list
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