BASIC 4K bug?

[bhall66]

Are there any known issues with the basic4k ROM on the IMSAI 8080? It seems mostly OK, but division and square root do not work on my system. For instance, "PRINT 2/3", which should return 0.6667, either crashes or returns a nonsense value. See below. Would anyone mind verifying this bug? If yours works, please share your configuration, thanks!

Here is an example:

LIST
0110 A=2
0112 B=3
0120 PRINT A
0130 PRINT B
0140 PRINT A+B
0150 PRINT A/B

RUN
2
3
5
13.2575

[pfcushing]

from what i can tell, 4k basic does not support floating point, only integer numbers, so your example is not a bug.. use 8k basic instead.

[bhall66]

That is a good thought. But I believe that floating point is supported (notice that BASIC 4K is giving a floating-point answer, not an integer answer).

Here is another BASIC 4K listing and run. It correctly handles floating point variables and their multiplication, but the division answer is incorrect. Am I doing something wrong? I cannot get SQR to work either.

LIST
0110 A=2.222
0112 B=3.333
0120 PRINT A
0130 PRINT B
0140 PRINT A*B
0150 PRINT A/B

RUN
2.222
3.333
7.40593
7.46611

[bhall66]

I am answering my own question. BASIC 4K division works fine as long as your machine is in 8080 mode. Since the software was written for the 8080 and not the Z80, everything is as it should be. If you test this for yourself, remember to issue a NEW command before doing anything else.

When I ported Altair BASIC, I found two instructions that work great on the 8080 but don't work the same on the Z80. I briefly looked at the Basic4k.asm source code for the same instructions but could not find a match. I bet it's something similar, though.