Anyone able to patch COMMAND.COM for me?

Champion (438)

26-04-2019, 10:48

Is anyone here able to create a patched COMMAND.COM for me? I want to completely hide the DOS boot process and start a COM file without the user noticing.

Hiding the MSX DOS version is easy (just replace the texts with 00's in MSXDOS.SYS). However, COMMAND.COM always shows "A>NAME.COM" if you launch a program using autoexec.bat. Also, on a MSX1 you get a date prompt (that needs to be skipped as well).

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By mtn

Champion (269)

26-04-2019, 11:00

Is this for some MSX barcade or something?

By wimpie3

Champion (438)

26-04-2019, 11:07

No, for my next MSXdev game.

By Pencioner

Scribe (1611)

26-04-2019, 11:21

i think the easiest way is to just find the bytes of string "COMMAND COM" in the MSXDOS.SYS file and replace with "MYGAME COM"

actually, there's a code which runs the COMMAND.COM and the name is hardcoded, so whenever you replace name - it should run your file instead. name is iirc already in FCB data format, so it is 11 bytes (8 for name padded with spaces at the end if shorter and 3 for extension). i remember i did something like that back in 1995 and it worked

By wimpie3

Champion (438)

26-04-2019, 11:58

@pencioner Yeah, I tried that too, unfortunately it seems COMMAND.COM loads up a few things in memory and cannot be left out. COMMAND.COM has to be launched first, BEFORE I can launch my COM game.

By larsthe18th

Master (192)

26-04-2019, 12:38

You can disable the screen in the bootsector of the disk, and put it back in when your game starts.
I used this trick in one of my projects

By wimpie3

Champion (438)

26-04-2019, 12:44

I've heard about this technique before. Would you be able to create me a MSX-DOS1 bootable DSK file with the screen disabled?

By larsthe18th

Master (192)

26-04-2019, 13:12

Sure, have uploaded a DSK image with the Disable screen in the bootsector,it boots to DOS.
Just boot up the DSK and type mode 80 to enable the screen.

By wimpie3

Champion (438)

26-04-2019, 13:49

Works perfect! Thanks a million!

By ericb59

Paragon (1126)

26-04-2019, 21:35

hello Larsthe18th,

How do you write your binary to the boot sector of a disk image ?

By NYYRIKKI

Enlighted (6093)

26-04-2019, 22:18

ericb59 wrote:

How do you write your binary to the boot sector of a disk image ?

Bootsector will be loaded to #C000 ... Entrypoint is #C01E IIRC... It is called two times. Once before RAM init and once after it. C-flag tells which call is in question.

... if you meant physically, please see BASIC DSKI$-function and DSKO$-instruction. (Sorry I can't link to DSKI$(), but there is link on DSKO$ page)