1. CS6401- OPERATING SYSTEMS L T P C 3 0 0 3

2. UNIT I OPERATING SYSTEMS OVERVIEW
Computer System Overview-Basic Elements, Instruction Execution, Interrupts, Memory Hierarchy, Cache Memory, Direct Memory Access, Multiprocessor and Multicore Organization. Operating system overview-objectives and functions, Evolution of Operating System.- Computer System Organization-Operating System Structure and Operations- System Calls, System Programs, OS Generation and System Boot.

3. What is operating system ?
It acts as an intermediary between a user of a computer and the computer hardware.
An operating system is a program that manages the computer hardware.
It also provides a basis for application programs.

4. purpose of an operating system
provide an environment in which a user can execute program
Exploits the hardware resources of one or more processors (cores)
Provides a set of services (system calls) to system users
Manages main/secondary memory and I/O devices

5. Goals of an Operating System
To make the computer system convenient to use.
To use the computer hardware in an efficient manner.

6. Components of a Computer System
Computer system can be divided into four components:
Hardware – provides basic computing resources
CPU, memory, I/O devices
Operating system
Controls and coordinates use of hardware among various applications and users
Application programs – define the ways in which the system resources are used to solve the computing problems of the users
Word processors, compilers, web browsers, database systems, video games
Users
People, machines, other computers

7. Four Components of a Computer System

8. Basic Elements Processor Controls the operation of the computer
Performs the data processing functions
Referred to as the Central Processing Unit (CPU)
Main Memory
Volatile
Contents of the memory is lost when the computer is shut down
Referred to as real memory or primary memory
I/O Modules
Moves data between the computer and external environments such as: Storage(e.g. hard drive),communications equipment (NIC)
System Bus
Provides for communication among processors, main memory, and I/O modules

9. Computer Components: Top-Level View

10. Instruction Execution
A program(instructions) to be executed by processor-stored in memeory
Two steps
Processor reads (fetches) instructions from memory
Processor executes each instruction