R (Register) - Change registers

Format: R {register=value : [N]flag }

     The command writes the value to the specified register or sets/resets
the specified flag. The following register names can be used:

       AX      BX       CX      DX       SP
       BP      SI       DI      DS       ES
       CS      SS       IP

For example, the command

        R AX=4E80

writes 4E80 to AX Register.

The following operations can be used to change processor flags:

     C - carry
     P - parity
     A - additional carry
     Z - zero
     S - sign
     I - interrupt
     D - direction
     O - overflow

Example:

 R NZ  - resets Z flag,
 R I   - sets interrupt flag.