Operating Systems: Resource Management

Resources and Their Management

• Components of a computer, viewed as resources, require effective allocation and management by the operating system (OS).
• The OS acts as an interface between application programs and hardware, controlling execution and resource distribution.

Operating System as "Shield"

• Users interact with the operating system instead of the hardware, which shields them from complex technical details.
• The OS provides structured functions for hardware access, ensuring safe usage by competent users.
• Key OS responsibilities include:
  • Program development support (editors and debuggers)
  • Program execution management
  • Input/Output device access
  • Controlled file access
  • Multi-user access handling
  • Error detection and response management
  • Resource utilization accounting

OS Management Dynamics

• The OS itself competes for hardware resources like the CPU, requiring it to manage its operations effectively.
• The OS must frequently relinquish control to user application software and utilize special hardware mechanisms to regain it.

Evolution of Operating Systems

• Operating systems evolve due to external and internal reasons.
• Evolution path includes:
  • Human Operator Phase: No OS; human operators handled computing tasks.
  • Serial Processing/Simple Batch Systems: Early OS mimicked human work behavior where each user program had to run entirely before the next could start.
  • Monitor Component: Responsible for recognizing program completion and preparing for subsequent jobs in a batch.

Monitor Control and Job Processing

• The resident monitor software stays always in memory to manage jobs.
• The monitor controls job sequencing, facilitating smooth transitions between user and monitor programs.
• The CPU cannot distinguish between executing user software or OS software; it processes both types of instructions.

Memory Management

• Control transitions indicate whether the CPU is executing user or monitor instructions.
• "Control is passed to a job" means the CPU executes instructions from a user program, while "control is returned to the monitor" indicates instructions from the monitor program are executed.

Additional Notes

• Consultation of Section 5.6 in the COS151 Textbook is recommended for a deeper understanding of program execution and monitor roles.
• Further details on the evolution and functioning of operating systems can be found in Section 2.2 of the textbook.