Layered Architecture for OS

• Organizes the OS as a hierarchy of layers -- one above the other
• THE system (1968) layers are organized as
  • Allocation of processor, switching between processes
  • Memory and drum management
  • Operator-process communication -- process and operator console
  • I/O management
  • User programs
  • Operator
• Multics
  • layers are organized as a series of concentric rings
  • inner rings more privileged