Operating Systems  A collection of programs that  Coordinates computer usage among users  Manages computer resources  Handle Common Tasks

O/S Functions  User Interface  I/O  Multitasking  Memory Allocation  Resource Sharing

Communication  You can manipulate stuff on another computer from your computer.  Security can require usernames and passwords to access systems, both local and remote.

Why are there Different Operating Systems?  Why are there different kinds of Cars or shoes?  Sometimes there are rationales such as pick-ups vs. SUVs vs. sub-compact sedans.  Sometimes the difference is cosmetic– Chevy vs. Ford vs. Honda …  Different O/Ss can serve different needs  Servers  Clients  Although servers and clients have different purposes the tasks that they perform can be similar as well as different.  Many variants of UNIX can be used as both clients and servers although they are probably configured differently.

Different O/S (continued)  But Windows 7, OS X Lion, and Ubunto Linux are all (normally) client operating systems.  Some operating systems are hardware dependent:  OS X can only be run (legally) on macintosh computers.  Windows cannot be run on (older) macintosh computers.  Some applications only run on a single platform:  Final Cut Pro is a NLE that runs only under OS X.  Vegas Video is a NLE that runs only under Windows.  Adobe Premiere is a NLE that runs under both platforms.

Multitasking  A process in which a computer apparently does two (or more) things at once.  Two ways of accomplishing this:  More than one processor (or more than one core)  Only one processor switching rapidly between tasks.  Since the CPU is much faster than i/o devices a computer executing only one process (such as word processing) would have the CPU idle most of the time.

Multitasking (continued)  Multitasking allows several programs to reside in memory simultaneously and switches the CPU between them.

Resource Management  CPU – if there’s more than one thread being executed the O/S switches between the processes.  RAM – the O/S allocates blocks of memory for programs being executed and for data being modified. When the O/S switches between apps, the O/S must “know” where the apps are located.  Virtual Memory – a technique that allows the system to use storage as if it were memory.

Resource Management (continued)  Hard Disk Space – The O/S has the responsibility to choose where on a disk to store data and programs.  Network Throughput -- The network connection on your computer constantly receives data and the O/S has to monitor the data and send it to the correct application.  External Devices – External devices such as a flash drive, keyboard, mouse, or webcam must function correctly when connected to the system. Device Drivers are programs that allow peripherals to work correctly. When you install a device it often comes with an installation disk which contains the device driver.

User Interface  How does the user interact with the computer?  For most computers today the user interface is graphical (GUI) characterized by WIMP.  GUIs are popular because they are both easy to use and easy to learn.  Since different operating systems and different programs use slightly different schemes it can be frustrating if you are changing from Windows XP to Vista or from Windows to OS X or from Office 2003 to Office 2007.

Booting  Booting – the process of starting a computer.  A Cold Boot occurs when a computer is booted by turning it on.  A Warm Boot occurs when you reboot or restart a computer that is already on. Older PCs had a reset button to allow one to restart the computer. Both Windows 7 and OS X have restart options on the start menu.  Normally rebooting will not be necessary unless your system “locks up” and your keyboard and or mouse becomes inoperable.

What Happens During a Cold Boot  When the power is turned on a program in ROM is run. This program tests the components of the computer to see if they are running properly.  If a problem is found a message is displayed on the screen. If no problem is found the process proceeds to the next step.  The computer then loads the operating system into memory and starts some behind-the-scenes programs called services.

What Happens during a Warm Boot  All processes are stopped, memory is cleared and the system is reloaded.  Depending on the operating system being used and the setup configuration, the computer may automatically load all programs that were running when the system was restarted.

Compatibility Between Operating Systems  Normally a program written for one operating system will not run on another operating system.  However, there may be “identical” versions for multiple operating systems. For example, FileZilla has versions for Windows and OS X, which look the same (more or less) and which function the same (more or less). But the windows version will not run on OS X and the OS X version will not run on Windows.  Data for similar programs is compatible. So if you write your project proposal using Word 2010 for Windows, I can load that data file into Word 2011 for Mac and read it with no problem.

O/S Compatiblilty and Disk Drives  Disk drives must be formatted to be used on a computer. There are several different formatting schemes that can be used.  FAT16 and FAT 32 are schemes that can be used for data storage on Windows, OS X, and Linux.  NTFS is a scheme particular to Windows.  HFS+ is a scheme particular to OS X.  Due to copyrights these schemes cannot be fully used (by the “wrong” computers).  Read accessiblilty/Write accessibility