/zi       Enables debug information in object file

          The /zi option tells Turbo Assembler to output complete
          debugging information to the object file. This includes
          line-number records to synchronize source code display and data
          type information to allow you to examine and modify your
          program's data.

          The /zi option lets you use all the features of Turbo Debugger
          to step through your program and examine or change your data
          items.

          You can use /zi on all your program's modules, or just on those
          you're interested in debugging.
          Since the /zi switch adds information to the object and
          executable programs, you might not want to use it on all your
          modules if you run out of memory when running a program under
          Turbo Debugger.