/j        Defines an assembler startup directive

          /jdirective

          The /j option lets you specify a directive that will be
          assembled before the first line of the source file.

          directive can be any Turbo Assembler directive that does not take
          any arguments, such as P286N, IDEAL, %MACS, NOJUMPS, and so on.

          You can put more than one /j option on the command line; they
          are processed from left to right across the command line.