If you use your computer via a purely graphical interface, you will typically double-click the Mathematica icon to start Mathematica. If you use your computer via a textually based operating system, you will typically type the command mathematica to start Mathematica.
|use an icon or the Start menu||graphical ways to start Mathematica|
|mathematica||the shell command to start Mathematica|
|text ending with Shift+Enter||input for Mathematica (Shift+Return on some keyboards)|
|choose the Exit menu item||exiting Mathematica (Quit on some systems)|
When Mathematica is first started, it displays an empty notebook with a blinking cursor. You can start typing right away. Mathematica by default will interpret your text as input. You enter Mathematica input into the notebook, then type Shift+Enter to make Mathematica process your input. (To type Shift+Enter, hold down the key, then press Enter.) You can use the standard editing features of your graphical interface to prepare your input, which may go on for several lines. Shift+Enter tells Mathematica that you have finished your input. If your keyboard has a numeric keypad, you can use its key instead of Shift+Enter.
You should realize that notebooks are part of the "front end" to Mathematica. The Mathematica kernel which actually performs computations may be run either on the same computer as the front end, or on another computer connected via a network. Sometimes, the kernel is not even started until you actually do a calculation with Mathematica.
The built-in Mathematica Documentation Center (Help ► Documentation Center), where you might be reading this documentation, is itself an example of a Mathematica notebook. You can evaluate and modify examples in place, or type your own examples.
To exit Mathematica, you typically choose the Exit menu item in the notebook interface.