I have a trouble with making TSR com file for DOS. It should set a new handler on a 21'th interrupt, terminate and stay resident. New handler should transfer control to an old interrupt 21h handler...

I've been trying to write TSR (Terminate-Stay-Resident) programs (in general) in Assembly (16-bit) for MS-DOS. I've read through a Wikipedia page on TSR and also a page on using it specifically in...

I would like to know how can we change the letters of the characters on screen using C. It is a TSR program using dos.h header file.