rdos/README.md
2019-10-08 10:24:36 +00:00

735 B

Memory Layout

On a 8080, there are no segments, the addresses are as displayed.

On on the 8086, a single segment with a value of 0x0100 is assumed. This implies that the first 4k of memory are not used.

The BDOS may be recompiled for starting at a lower address, in this case, the minimum memory requirement may be less than 64k.

Start Size Function
0xF000 4k BDOS and hw drivers
var BDOS data
SP var Stack, growing down
Free memory
0x0100 up to stack Transient Program Area
0x0080 128 bytes Command line and disk buffer
0x0000 128 bytes System data area

Application program interface

It is using the call 5 convention with CP/M compatible syscall numbers.

File I/O is done via FCB blocks.