% n or Out[n] is a global object that is assigned to be the value produced on the n\[Null]^th output line. % gives the last result generated. %% gives the result before last. ...

Subsuperscript[x, y, z] is an object that formats as x_y^z.

VerticalSlider[y] represents a vertical slider at position y with range 0 to 1. VerticalSlider[Dynamic[y]] takes the position to be the dynamically updated current value of ...

$HistoryLength specifies the number of previous lines of input and output to keep in a Mathematica session.

In doing a calculation with Mathematica, you usually go through a sequence of steps. If you want to, you can do each step on a separate line. Often, however, you will find it ...

DialogInput[expr] interactively puts up expr as a dialog notebook, waits until a DialogReturn[e] is evaluated from within it, and then returns the result e. DialogInput[{x = ...

AddVertex[g] adds one disconnected vertex to graph g. AddVertex[g, v] adds to g a vertex with coordinates specified by v.

Strong is an option to ConnectedQ that seeks to determine if a directed graph is strongly connected.

Weak is an option to ConnectedQ that seeks to determine if a directed graph is weakly connected.

Align Selected Graphics makes selected graphics cells line up with the first graphic in the selection.