You can use files on your computer system to store definitions and results from Mathematica. The most general approach is to store everything as plain text that is ...

An expression like x^2+2x-7==0 represents an equation in Mathematica. You will often need to solve equations like this, to find out for what values of x they are true. This ...

"CopySpecial" is a front end token that converts the selection to a specified format and copies it to the clipboard.

Automatic Numbering creates an automatic numbering object, or counter, in the current notebook.

Initialization Cell makes a cell auto-evaluate whenever the notebook is opened and the kernel is launched.

Initialization Group makes the cells in a group auto-evaluate whenever the notebook is opened and the kernel is launched.

CellOpen is an option for Cell that specifies whether the contents of a cell should be explicitly displayed.

ControllabilityGramian[ss] gives the controllability Gramian of the StateSpaceModel object ss.

CurrentImage[] returns the current image captured from a connected camera.CurrentImage[n] returns n sequential image frames as a list.

DefaultDuplicateCellStyle is a notebook option that specifies the default style to use for cells created by automatic duplication of other cells in the notebook.