Syllabi and Basics

OS is a special software layer that provides and manages the access from apps/users to hardware resources (CPU, memory, disk, etc).

The Role of OS

OS as referee

• Resource Allocation: multitasks on constrained resources.

• Isolation: fault in one app shall not disrupt others.

• Communication: realiable, safe and fast.

OS as illusionist

Illusion of resources not physically present.

OS as glue

• Providing common services to facilitate resource sharing, like reading/writing files, sharing memory, and passing messages.

• Decouple hardware and app development: most applications can evolve independently with OS, unless those require very low-level programming such as databases.

The Goal of OS

• Managing hardware resources
  • Allocating resources to concurrent tasks, who gets more?
  • Determining hardware status: CPU frequency, I/O device on/off, etc.
• Facilitate app developers
  • Illusion of resources not physically present
  • Isolation of apps
  • Cross-apps communication
• Facilitate users
  • UI components and rendering