Pokeb()

         Stores a byte at a memory position

    Syntax:

         Pokeb( nSegment, nOffset, nByte ) -> Nil

         nSegment : Memory Segment
         nOffset  : Memory Offset
         nByte    : Byte to store

    Description:

         DANGER!!
         This function allows low level access to system. It should be used
         with extreme care and requires a thorough knowledge of computer
         Architecture.

    Return:

         Nothing.

    Example:

         Pokeb ( 64, 0, 16 )                    // 0040:0000h = 0Fh