Giving input to Mathematica

The simplest way to use Mathematica is like a calculator. The range of
caluclation that can be performed are far greater than a conventional
calculator! Mathematica has over 750 built in mathematical operations.
In addition to that, Mathematica offers symbolic and graphical
computations.

You can type in a calcualtion and Mathematica will print back the
answer. At the In[1]:= prompt you can enter the input and hit Return
or Enter. Mathematica will then process you input and give you the
answer. The text on the lines starting with In[n]:= is where you give
the input and the lines labelled as Out[n]= is what Mathematica prints
back. 

Mathematica can accept commands that extend over many lines. In the
case of the input expression being not syntactically corrent,
Mathematica simply waits for you to provide it with further input,
rather that computing the result upto the position of the cursor. When
expecting more input, the cursor appears several spaces from the left
edge of your terminal screen. For example, entering '2 + 3 +' on the input
line and hitting returns prompts Mathematica to wait till syntax is
complete. Entering 4 on the next line completes it and the result will
be printed out.

	In[4]:= 2 + 3 +
	        4

	Out[4]= 9

If you wanted to abandon the input, you can hit Return twice in succession.