ctrl-alt-del

When the value in this file is 0 (the default), ctrl-alt-del is trapped and sent to the init program to handle a graceful restart (or to the PID of your choice, which you can configure with cad_pid tunable). However, when the value is greater that zero, Linux's reaction to this key combination will be an immediate reboot, without syncing its dirty buffers.

When a program (like dosemu) has the keyboard in raw mode, the ctrl-alt-del is intercepted by the program before it ever reaches the kernel tty layer, and it is up to the program to decide what to do with it.