Operating Systems Chapter 1

What is an Operating System?

A program that acts as an intermediary between a user of a computer and the computer hardware.

The operating system is responsible for the following activities in connection with process management:

Creating and deleting both user and system processes Suspending and resuming processes Providing mechanisms for process synchronization Providing mechanisms for process communication Providing mechanisms for deadlock handling

Operating system goals:

Execute user programs and make solving user problems easier. Make the computer system convenient to use.

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

OS is a resource allocator

Manages all resources Decides between conflicting requests for efficient and fair resource use

Computer-system operation

One or more CPUs, device controllers connect through common bus providing access to shared memory Concurrent execution of CPUs and devices competing for memory cycles

Security

defense of the system against internal and external attacks

OS is a control program

Controls execution of programs to prevent errors and improper use of the computer

Protection

any mechanism for controlling access of processes or users to resources defined by the OS

Caching

copying information into faster storage system; main memory can be viewed as a last cache for secondary storage.