Sinclair ZX80 / ZX81 / Z88 Forums

The "28" should perhaps be "128" to clear the sign bit for positive numbers?

Here is a version that uses RAM in 8192-16383 as workspace, can be compiled with MCODER II, and run with LET L=USR 20500:

Interesting! Would this be something for MCODER?

First, belated hellos from me to everyone as well! It is really nice to read about everyone's projects. Here is just something funny my brother discovered in the early 80s. Usually RAND USR n where n is a random address in the ROM crashes the ZX81. But for n=975, something interesting happens; scree...

In the emulator available here http://rullf2.xs4all.nl/sg/z81-2.2.tar.gz I've added a startup flag (-f) so that the six bytes after a number are not stored in the BASIC program when lines are entered. Programs still run, but of course more slowly. Just for fun, to see what changes are needed to the ...

There are 24 numbers in the first 90 that are prime or can be divided by 7. Primes 2, 3, and 5 are quickly handled in lines 80 and 82. There would be more ways to construct a candidate list, smaller or larger than 24. A list X with four elements would be 3, 7, 9 and 11, numbers that are prime or can...

It is a form of "trial division" (http://en.wikipedia.org/wiki/Trial_division) where the candidate factors are mostly prime when C=0 and with less prime candidates as C increases. Here is a slightly shifted version of the 24 families. For C=0, the 24 numbers contain all numbers except those that can...

There are some notes in the README in section 4; uncomment the following lines at the beginning of the Makefile and set PREFIX as desired:

According to the Makefile, data should be relative to the prefix, and if the prefix is absolute, the path to the data will be too - did you recompile after editing the Makefile and a make clean?

I haven't tried this, but I think you can set such paths by editing the Makefile?