I'm writing my own BASIC from scratch in 8088 assembly. The editor, the way the lines are stored and can be listed again seems to work fine. The next step is to write the code for the various commands and functions. I want to support at least the commands and functions as supported by the C64. This means I need to support floating point.

I have found documentation about FP plus some info about adding, subtracting, multiplication an division using FP numbers. But I haven't found anything related to LOG, SIN, square root and other more difficult stuff yet. Any pointers, please?

Best would be if somebody has 8088 code that goes by it. 80836+ code would do as well, I should be able to convert it to 8088, but no 80x87 code: it should run on a standard IBM-PC in the first place.

One thing I'm thinking about is looking how the c64 does it. I "only" have to translate the 6502 code into 8088. And here is a challenge as well: single precision is 32 bits, double precision is 64 bits but the C64 supports 40 bits.
Using 40 bits as well means less work but using 64 bits could mean that the BASIC as whole will be slowed down. I have no idea what precision the original IBM BASIC (= Microsoft) uses.

Any help and info is welcome!