INT 03H: Breakpoint Interrupt

 The INT 03H vector is used by debugging utilities in order to intercept
 execution when it reaches a user-selected address.

 The opcode for INT 03H is one byte (c0H), so it can lay over top of the
 start of any CPU instruction, without any chance of overwriting the code
 that follows it.

See Also: ROM-BIOS Functions
          DOS Functions