Monolithic Structure for OS

• Most primitive form of the OS
• Practically no structure
• Characterized by a collection of procedures that can call any other procedure
• All procedures must have a well-defined interface
• Does not allow information hiding (private functions for procedures)
• Services provided by putting parameters in well-defined places and executing a supervisory call.
• Basic structure
  • Main program that invokes requested service procedures
  • Set of service procedures to carry out system calls
  • Set of utility procedures to help the service procedures
• User program executes until
  • program terminates
  • program makes a service request
  • a time-out signal occurs
  • an external interrupt occurs
• Problems with monolithic structure
  • Difficult to maintain
  • Difficult to take care of concurrency due to multiple users/jobs