Fat

Our FAT32 driver now supports byte-wise writing of a file. Reason enough to continue reworking the file handling of our EhBasic port that we started here to finally having the SAVE command write ASCII source files.

The basic idea is to open a file, redirect the EhBasic output vector to our new kernel call “krn_write_byte”, then trigger the LIST command internally. The listing being output by LIST will then be written to the opened file instead the screen. Finally, once LIST is done writing, close the file and return.

Since our implementation of FAT32 now supports reading a file byte for byte, a little rework of the file handling in our version of EhBasic is in order.

In the past, we only could read or write a file as a whole, relative to the location in memory where the according pointer pointed to. We used this in EhBasic to save and load BASIC programs by dumping and reloading it’s binary representation from memory. While this works well, this approach has the major disadvantage that the saved program will be incompatible with other versions of EhBasic or even with our own when the token list is changed, which happens when adding new commands.