single ascii character that causes DOS to reboot

[jafir]

So years ago, in the days of dialing up to a BBS, I recall downloading either Darkstar BBS or maybe it was the graphical client that connected to it. I recall there being a batch file that, in certain conditions, would echo a single character (if I'm remembering correctly) to a new file named reboot.com and then would execute that file and the computer would reboot. I think it was one of the line drawing characters, like what you'd get if you press alt-183, but I don't recall the exact character and I'm having trouble finding the software, because it might have been the beta software that never got officially released.

Does anyone know of this trick, and what character that would be?

 

[Chuck(G)]

I know of DOS one-liners that reboot (e.g. echo g=ffff:0 | debug), but it would take 2 characters to reboot DOS as an executable COM file, I'd think.

 

[Trixter]

Correct, there is no single opcode by itself that reboots a PC. "CD 19" is 2 bytes (INT 19h) and that would work. JMP FFFF:0 is a single line that would also work, but it's 5 bytes.

 

[VileR]

Was thinking that echoing CDh to a text file might automatically append a ctrl-Z as an EOF marker, but that's 1Ah, not 19h. One character off...

 

[jafir]

It’s certainly possible (and probable) that I’m misremembering that it was one character when it was really two. I tried echo alt 205 alt 025 > reboot.com and it seems to do a fast reboot, no POST, just boot.