Mathematica documents are often called "electronic notebooks" and consist of a sequence of pairs of input and output cells. A cell is where you enter a Mathematica command or receive output from the program.
Open the Mathematica program on your computer. You should see an empty notebook without any cells. Click the mouse somewhere on the notebook to activate the cursor. Then type
2 + 2and press the Enter key on the numeric keypad. You should see a bracket appear at the right edge of the notebook window. This bracket defines the extent of the input cell you just created. Throughout this tutorial the indented lines represent Mathematica input and output. Boldface lines will represent the input you type into a Mathematica notebook. Mathematica automatically puts your output into boldface, so your Mathematica notebook should look very similar to the indented lines in this tutorial.
Pressing the Enter key instructs Mathematica to evaluate the input cell that contains the cursor. (Make sure the cursor is in an input cell, or else Mathematica won't do anything when you press Enter.) In this case, we are asking Mathematica to evaluate the expression 2 + 2. After some time, an output cell will appear in your notebook with the result:
4Notice that the input and output cells are labeled "In" and "Out". Each has its own bracket, and they are grouped together by an outer bracket.
It may seem that it took Mathematica a long time to perform this simple calculation. This is because Mathematica loads into your computer in two stages. When you open the Mathematica icon, the user interface portion of the program is loaded. The part of the program that actually does calculations doesn't get loaded until the first time you press Enter.
You can use the mouse to copy text from a previous input cell and paste it into the current input cell. This is useful if you want to repeat a portion of an earlier calculation or if you need to correct a spelling mistake. Just make sure the cursor is in the current input cell before you press Enter.
Other parts of the Mathematica tutorial: