Computer Operating Systems

The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. 

Files created on a computer in one operating system may not be compatible on computers running a different operating system.


DOS stands for Disk Operating System and was produced by Microsoft.  DOS was in wide use from about 1981 to 1990.  DOS was text based.  If you wanted to copy a file you had to type the copy command.  If you wanted to run a program you had to know the exact name of that program.  Computers running DOS were difficult to upgrade.  Computers running DOS were difficult to operate.


Text based operating system mainly for large servers.  


Text based operating system developed by Finnish student Linus Torvalds (1991).  Linux is FREE.  Linux is not especially easy to use.  You can run a GUI in Linux to make it look more like Windows.


The Mac operating systems has long been know to be very friendly and stable.  The latest version of this OS is based on Unix.

MS Windows

Windows 1.0 (1985)

Windows 3.0 (1990)

Windows 95 (1995):  Uses a completely different GUI.  Supports 32-bit applications.  Abandons 8 character filenames. Uses Plug & Play which makes adding hardware much easier.  Reliability:  medium to low (ie. computer crash is not too unusual).

Windows NT (1993):  32-bit.  Windows NT is not based on Windows 95.  Designed for secure business environments.  No Plug & Play.  Windows NT is a very stable platform (very few crashes)

Windows 98 (1998):  Windows 98 is based on Windows 95.  Looks similar to Win95.  Much improved Plug & Play.  Better reliability.

Windows ME (2000) : (Millenium Edition) Windows ME is also based on Windows 95.

Windows 2000 (2000):  Based on the NT platform.  Aimed at business users.

Windows XP (2001) :  Based on the NT platform.  Aimed at home users.