Using a TextBased Interface
The standard front end interface, as discussed in "
Using a Notebook Interface", is appropriate for most users' purposes. In some cases, however, you may not need to use the notebook front end, and you may want instead to interact more directly with the
Mathematica kernel. You can do this by using a textbased interface, in which text you type on the keyboard goes straight to the kernel.
It is important to note that while the textbased interface provides access to most of the capabilities of the
Mathematica kernel, the graphics functionality and dynamic interactivity of the
Mathematica front end are not available.
To start
Mathematica with a textbased interface, you typically type the command
math at an operating system prompt. On some systems, you may also be able to start
Mathematica with a textbased interface by doubleclicking a
Mathematica kernel icon.
math  the operating system command to start Mathematica 
text ending with Enter  input for Mathematica 
Ctrl+D or Quit[]  exiting Mathematica 
Running Mathematica with a textbased interface.
A dialog with
Mathematica using a textbased interface.
In[1]:= 2^100
Out[1]= 1267650600228229401496703205376
In[2]:= Integrate[1/(x^3  1), x]
1 + 2 x
ArcTan[] 2
Sqrt[3] Log[1 + x] Log[1 + x + x ]
Out[2]= () +   
Sqrt[3] 3 6
At each stage,
Mathematica prints a prompt of the form
In[n]:= to tell you that it is ready to receive input. You can then type your input, ending with
Enter or
Return.
When you have entered your input,
Mathematica will process it and generate a result. If it prints the result out, it will label it with
Out[n]=.
In
Mathematica documentation, "dialogs" with
Mathematica are often shown in the following way:
The computer prints In[1]:=. You just type in 2+2. The line that starts with Out[1]= is the result from Mathematica.
Out[1]=  

Note that you do not explicitly type the
In[n]:= prompt; only type the text that follows this prompt.
Most of the actual dialogs given in the
Mathematica tutorials show output in the form you get with a notebook interface to
Mathematica; output with a textbased interface looks similar, but lacks such features as special characters and font size changes.
If your input is short, then you can give it on a single line. If your input is longer, you can give it on several lines.
Mathematica will automatically continue reading successive lines until it has received a complete expression. Thus, for example, if you type an opening parenthesis on one line,
Mathematica will go on reading successive lines of input until it sees the corresponding closing parenthesis. Note that if you enter a completely blank line,
Mathematica will throw away the lines you have typed so far, and issue a new input prompt.
%n or Out[n]  the value of the n^{th} output 
In[n]  the n^{th} input, for reevaluation 
Retrieving and reevaluating previous input and output.
With a textbased interface, each line of
Mathematica input and output appears sequentially. Often your computer system will allow you to scroll backwards to review previous work, and to cutandpaste previous lines of input.
But whatever kind of computer system you have, you can always use
Mathematica to retrieve or reevaluate previous input and output. In general, reevaluating a particular piece of input or output may give you a different result than when you evaluated it in the first place. The reason is that in between you may have reset the values of variables that are used in that piece of input or output. If you ask for
Out[n], then
Mathematica will give you the final form of your
n^{th} output. On the other hand, if you ask for
In[n], then
Mathematica will take the
n^{th} input you gave, and reevaluate it using whatever current assignments you have given for variables.
To exit
Mathematica, type
Quit[] at an input prompt. You may also exit
Mathematica by typing
Ctrl+D or
Ctrl+Z, depending on your computer system.