Runcom support DOS .com binary files and boot sector files.

1- The DOS .com support

Runcom provides few BIOS and DOS (int 21H) interrupt handlers. Many .com files
may not work. DOS .exe are also supported.
You can test it with the file /usr/bin/debug.com, with the command line :
$ debug.com

2- The boot sector image support

A boot sector image is a 512 bytes file ending with the 0xAA and 0x55 bytes 
with the .bin extension.
Bios disk (int 13H) are emulated (CHS or LBA) with an image file :
- hard disk are image ./hd0, ./hd1, ... for disk 0x80, 0x81...
- floppy disk are image ./fd0, ./fd1 ... or /dev/fd0, /dev/fd1 if not found.
You can test it with the file /usr/bin/debug.bin, with the command line :
$ debug.bin

3- The 512 bytes boot sector debugger /usr/bin/debug.bin

Usage:

 f DX:CX		load one CHS sector to 0000:7C00
 t			trace one step
 g <address>		go to adrs
 d <address>		display 16 bytes, CR for next 16 bytes...
 e <address> <words>...	enter memory byte/word/dword
 m <segment>		self move
 + <segment>		default segment offset

seqment and offset are hexadecimal values in 0..FFFF range
address is linear hexadecimal value in 0..FFFFF range or seqment:offset
words are bytes in 0..FF range or words in 000..FFFF range or double words
CX and DX are used by INT13H/AL=01 BIOS interrupt.

Example:
 m 0FC0			move debugger to 0FC0:0000 0FC0:01FF
 f 1			read floppy boot sector to 0000:7C00
 f 80 1			read hard disk master boot sector to 0000:7C00
 g 7C0E			...