CS6401- OPERATING SYSTEMS L T P C 3 0 0 3
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.
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.
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
Goals of an Operating System To make the computer system convenient to use. To use the computer hardware in an efficient manner.
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
Four Components of a Computer System
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
Computer Components: Top-Level View
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