What is an Operating System?

Operating System The operating system manages computer hardware and software Also provides common system services for applications OS functions: Kernel Interface between software and hardware like RAM and input/output devices Program execution Create a process to assign memory and other resources for use by the application Interrupt handling Components outside the CPU, like keyboard and network, need to get the attention of the software in “real time”

Operating System OS functions: Memory management Multi-tasking Assign memory for an application to execute in, and isolate it from other application memory Multi-tasking Most operating systems allow multiple programs to run simultaneously OS allocates CPU time in a rotating scheme to each active application Multi-tasking is a bit of an illusion, only one set of instructions can execute in a CPU at a time Disk access (file system) File system access (read or write) is mediated by the operating system This mediation includes a check that the user has privileges to access that file

Operating System OS functions: Device drivers Networking Security The machine level software for display or keyboard or network Networking Local network interface (Ethernet) protocols External network interface (TCP/IP) protocols Security User authentication and authorization User name and password (more on passwords below) Protect system resources (files) from unauthorized access User permissions can be given to files and folders If authenticated user doesn’t have permission they can’t access the file User interface (GUI or shell) How the user starts an application or program

Common Operating Systems Unix – one of the original operating systems Linux – free, open source derivative of Unix (Ubuntu) Mac OS x – for Apple Macintosh computers only iOS – Apple mobile Android – Google mobile Windows – Microsoft, runs on multiple hardware, most widely used Main frame operating systems OS stats - http://www.w3schools.com/browsers/browsers_os.asp

Password Security http://geekbeat.tv/why-password-security-is-so-important/ http://security.stackexchange.com/questions/65065/how-important- it-is-to-change-password-regularly