This paper discusses the operating system written in single language “Mesa” and designed for the single user machine along with network-based distribution system. Operating system which is more flexible and secure using defensive protections. It provides set of features to support high level programs in Mesa Language. Paper describes mesa as a modular language where the high level programs are constructed with two modules, program module and definition module. Program modules are connected with two types of interfaces public for clients (files, virtual memory, streams, network communication etc.) and private interface (implementation).


In view of emerging trend for personal computers, author aims to create a powerful single user system with all the important features required for user an experience. Where, at the time multi-user systems were point of interest which uses the timesharing and reserved resources.


  • Shared virtual memory introduced for file system and ‘Space’ interface for virtual memory allocation.
  • Pilot supported a large available storage (~ 10^13 bits)
  • Network based distributed systems where computers connect with each other.
  • Unique 64 bit universal identifiers was used to identify the distinct files across different machines.
  • With the help of advising operations such as Space. Activate, Space. Deactivate, Space. Kill tunes heavy traffic periods by eliminating unnecessary transfers, by scheduling the disk arm efficiently and by ensuring that during the visit to a given arm position all of the appropriate transfers takes place.
  • It provides software drivers for a variety of networks.


  • Protection is week.
  • Imposing further structure on files and volumes
  • Fine grained allocation of Spaces.
  • Protection against dangling references
  • Providing reliability of data transfer.

Extra Question:

Protection in a single-user computer should not be an issue because there is no need for ownership or permission issues.