Process Model

Sequential Processes

• Also known as a task
• Essentially a program in execution
• Consists of
  • Program code
  • Current activity (defined by program counter)
  • Process stack
    • Subroutine parameters
    • Return addresses
    • Temporary variables
  • Data section
    • Global variables

Concurrent Processes

• Multiprogramming
• Physical resource sharing
  • Required due to limited hardware resources
• Logical resource sharing
  • Concurrent access to the same resource, such as a file
• Computation speedup
  • Break each task into subtasks
  • Execute each subtask on a separate processing element
• Modularity
  Division of system functions into separate modules
• Convenience
  • Perform a number of tasks in parallel
• Real-time requirements for I/O