This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.1)

Controlling the Display of Large Expressions

When you do symbolic calculations, it is quite easy to end up with extremely complicated expressions. Often, you will not even want to see the complete result of a computation.
If you end your input with a semicolon, Mathematica will do the computation you asked for, but will not display the result. You can nevertheless use % or Out[n] to refer to the result.
By default, the Mathematica front end will display any outputs which are excessively large in a shortened form inside an interface which allows you to refine the display of the output.
Mathematica shows this output with 5138 of the terms omitted.
Click for copyable input
The Show Less and Show More buttons allow you to decrease or increase the level of detail to which Mathematica shows the expression. The Show Full Output button removes the interface entirely and displays the full result, but the result may take considerable time to display. The default threshold size at which this feature starts working may be set using the Set Size Limit option, which opens the Preferences dialog to the panel with the appropriate setting.
The large output suppression feature is implemented using the Mathematica function Short. You can use Short directly for finer control over the display of expressions. You can also use it for outputs which are not large enough to be suppressed by the default suppression scheme.
Ending your input with ; stops Mathematica from displaying the complicated result of the computation.
Click for copyable input
You can still refer to the result as %. //Short displays a one-line outline of the result. The <<n>> stands for n terms that have been left out.
Click for copyable input
This shows a three-line version of the expression. More parts are now visible.
Click for copyable input
This gives the total number of terms in the sum.
Click for copyable input
command;execute command, but do not print the result
expr//Shortshow a one-line outline form of expr
Short[expr,n]show an n-line outline of expr

Some ways to shorten your output.