On Fri, May 3, 2024 at 7:49 PM Paul Koning via cctalk <cctalk@classiccmp.org> wrote:
> BASIC-PLUS (part of RSTS) had a weird floating point history. The original > version, through RSTS V3, used 3-word floating point: two words mantissa, one > word exponent. Then, presumably to match the 11/45 FPU, in version 4A they > switched to your choice of 2 or 4 word float, what later in the VAX era came > to be called "F" and "D" float. Interesting. The original (pre-Series II) HP 3000 systems in the mid 1970s also started with a three (16-bit) word floating point format and later switched to supporting both 2 and 4 word formats. One of the only ways you would see this is in the header line that displays when you run BASIC:: :BASIC HP32101B.00.26(4WD) BASIC (C)HEWLETT-PACKARD CO 1979 > The "4WD" (as opposed to "3WD") tells you you're on a machine that uses the four word long floating point.
