Where starts program from ATR or CAS file?

[fandango2021]

Hello!

 

When I load an ATR or CAS file to Altirra, where is loaded the first instruction in memory (like the main function from C)? How do I know that? From the ATR or CAS file? Or is predefined by the emulator?

 

Thanks!

[Wrathchild]

Typically anywhere between $480 and the top of memory, e.g. $BFFF. However you can load a bootstrapper that can move loaded memory into an extended bank or in the memory under the OS.

Will also depend on whether you are using an existing DOS too.

Have a search on the forum for LOWMEM and you come across discussions on the topic.

Edited December 11, 2021 by Wrathchild

[vitoco]

The boot record from the ATR or the CAS is loaded in buffer location $400 (128 bytes), then copied to wherever address the word from bytes 2 and 3 (starting from 0) points to. The following sectors/blocks are also loaded from the device into $400 and then copied contiguous to the previous one. The total number of sectors to read is stored in byte 1 of the boot record, and the run address is at byte 6 of the first record (starting from 0 again).

 

Edited December 11, 2021 by vitoco

[fandango2021]

Thanks!