What are operating systems?

Functions of Operating System

An operating system is oversee hardware use.

1. Directs operational resource

control use of CPU, memory, peripheral devices.
hardware resource be allocate applications.

2. Enforces working policies

fair resource access, limits to resource usage.

3. Mitigates difficulty of complex tasks

abstract hardware details. (system calls)

Operating System Definition

• Directly has privileged access to the underlying hardware
• Hides the hardware complexity
• Manages hardware on behalf of more applications according
• It Ensures that applications are isolated and protected from one another

Operating System Examples

Desktop Environment

• microsoft Windows
• UNIX based
  • mac OS X (BSD)
  • Linux
  • Ubuntu

Embedded Environment

• Android
• OS
• Symbian

OS Elements

• Abstractions (Managed the harddisk and memory etc hardware resources)
  • process, thread, file, socket, memory page
• Mechanisms (Application access to hardware resource)
  • create, schedule, open, write, allocate
• Policies (How do mechanisms will be used to manage the access to hardware)
  • last-recently used (LRU), earliest deadline first (EDF)