UNIT - 1
Roadmap • What is an Operating System?
• • • • • • • • Operating System Objectives/Functions The Evolution of Operating Systems Major Achievements Structuring methods Design of API’s Interrupts Device Organization User/System state Transition
What is an Operating System? • A program that acts as an intermediary between a user of a computer and the computer hardware. OR
• A program that controls the execution of application programs. • Kernel – the one program running at all times (all else being application programs).
OR • Resource allocator – manages and allocates resources. • An interface between applications and hardware
Main objectives of an OS: • Convenience
Make the computer system convenient to use.
An OS allows the computer system resources to be used in an efficient manner
• Ability to evolve
An OS should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions without interfering with service.
Abstract View of System Components
Services Provided by the Operating System • Program development
Editors and debuggers.
• Program execution
OS handles scheduling of numerous tasks required to execute a program.
• Access I/O devices
Each device will have unique interface OS presents standard interface to users
• Controlled access to files
—Accessing different media but presenting a common interface to users —Provides protection in multi-access systems
Services cont… • System Access • Error detection and response
—Internal and external hardware errors —Software errors —Operating system cannot grant request of application
—Collect usage statistics —Monitor performance
The Role of an OS • A computer is a set of resources for the movement, storage, and processing of data. • The OS is responsible for managing these resources.
Operating System as Software
The OS functions in the same way as