Abstract View of Operating System By Mr Ajit

Abstract View of Operating System By: Mr. Ajit B. Patil KIT’s College of Engineering Kolhapur

Content • Abstract views • A designer’s abstract view of an OS • Fundamental principles of OS Operation

Abstract views • An abstract view focuses on the essential characteristics of a system – It contains some selected characteristics, and ignores others • It helps to control complexity in designing and understanding a system – For example, two abstract views of a car: • The driver’s view contains the rear-view mirror, steering, gear shift, and speedometer but ignores engine details • The mechanic’s view contains fluid levels, electrical system, … Q: Give examples of abstract views A: View of an abstract data type, object, . .

A designer’s abstract view of an OS • User interface: Accepts commands from users: GUI, command line interface • Non-kernel programs: Implement user commands • Kernel: Core of the OS─controls the computer, provides functions & services

A designer’s abstract view of an OS • The abstract view consists of three components – The kernel programs • interact with the computer’s hardware and implement the intended operation – The non-kernel programs • implement creation of programs and use of system resources by them. These programs use kernel programs to control operation of the computer – The user interface • interprets the commands of a user and activates non-kernel programs to implement them

Fundamental Principles of OS Operation • The kernel of the OS is the collection of routines that form the core of the operating system – Controls operation of the computer by Implementing task control functions – Set of services to user programs – Exists in memory during operation of the OS • An interrupt diverts the CPU to execution of the kernel code • A software interrupt is used by programs to communicate their requests to the kernel

Fundamental Principles of OS Operation (continued) • CPU has two modes of operation: – Kernel mode • CPU can execute all instructions • Kernel operates with CPU in this mode so that it can control computer operations – User mode • CPU cannot execute instructions that could interfere with other programs or with the OS if used indiscriminately • CPU is put in this mode to execute user programs