Thus the basic functions of an OS are –
1. Process Management – Managing the programs that are running. 2. Memory Management – Managing and rationing the memory between processes and data. 3. Storage Management – Managing the permanent Storage of data on disks or other media 4. I/O Management – Managing the input and output
5. Device / Resource Management – Managing devices and resources and allowing the users to share the resources 6. Security and Protection – Securing the system against possible unauthorized access to data or any other entity. Protecting the parts of the system against damage. 7. Booting the System and getting it ready to work.
8. Data communications – Providing interface to connect to other computers or allowing others to connect Definition:
An operating system is a collection of software that coordinates the working of the different components of the system and gets the user’s job done. The operating system provides the user with all the basic things necessary to do his job. What does an os do??
* An Operating System exploits the hardware resources of one or more processors to provide a set of services to system users. * An Operating System also manages secondary memory and input/output devices on behalf of its users. Process Control Block:
A data structure by which the system identifies a process.
It contains -
* Identifier: A unique integer associated with a process
* State : A currently executing process is in running state * Priority : Priority level relative to other processes
* Program counter : Address of the next instruction of the program to be executed.
* Memory pointers: pointers to the program code and data associated with the process, and any shared memory blocks * Context data: Data in the registers in the processor during process execution.
* I/O status information: outstanding I/O requests, I/O devices allocated to the process, a list of files...
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