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  For the most part, DOS users--not DOS programmers--benefit most from DOS
  version 4. DOS version 4 support for expanded memory and larger fixed
  disks makes it easier for applications to take advantage of these
  resources. The full-screen command shell clearly resembles the command
  interface provided with OS/2 Presentation Manager and reflects the
  philosophy that the point-and-shoot graphics interface is what PC and PS/2
  users want. But from a programmer's point of view, DOS version 4 support
  for these features presents few novelties.

  DOS version 4 isn't revolutionary. It represents a logical step in the
  evolution of the predominant operating system for the IBM PCs and PS/2s.