Introduction to Operating Systems

What is an operating system?

• Tool to make programmer's job easy
• Resource allocator
  • Must be fair; not partial to any process
  • Must discriminate between different class of jobswith different service requirements
  • Do the above efficiently
• Control program
• Tool to facilitate efficient operation of computer system
• Virtual machine that is easier to understand and program
• Layered architecture

• Early Systems
• Second Generation Systems
• Third Generation Systems
• Fourth Generation Systems

Operating System Concepts

• Kernel
• Processes
• Threads
• Files
• System calls
• Shell

• Minimal operating system
• Monolithically structured operating system
• Layered operating systems
• Virtual machines
• Process hierarchy
• Client-Server model