This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.2)

Mathematical Notation in Notebooks

If you use a text-based interface to Mathematica, then the input you give must consist only of characters that you can type directly on your computer keyboard. But if you use a notebook interface then other kinds of input become possible.
There are palettes provided which operate like extensions of your keyboard, and which have buttons that you can click to enter particular forms. You can access standard palettes using the Palettes menu.
Clicking the button in this palette will enter a Pi into your notebook.
Clicking the first button in this palette will create an empty structure for entering a power. You can use the mouse to fill in the structure.
You can also give input by using special keys on your keyboard. Pressing one of these keys does not lead to an ordinary character being entered, but instead typically causes some action to occur or some structure to be created.
Esc p Escthe symbol
Esc inf Escthe symbol
Esc ee Escthe symbol for the exponential constant (equivalent to E)
Esc ii Escthe symbol for (equivalent to I)
Esc deg Escthe symbol ° (equivalent to Degree)
Ctrl+^ or Ctrl+6go to the superscript for a power
Ctrl+/go to the denominator for a fraction
Ctrl+@ or Ctrl+2go into a square root
Ctrl+Spacereturn from a superscript, denominator or square root

A few ways to enter special notations on a standard English-language keyboard.

Here is a computation entered using ordinary characters on a keyboard.
Click for copyable input
Here is the same computation entered using a palette or special keys.
Click for copyable input
Here is an actual sequence of keys that can be used to enter the input.
Click for copyable input
In a traditional computer language such as C, Fortran, Java or Perl, the input you give must always consist of a string of ordinary characters that can be typed directly on a keyboard. But the Mathematica language also allows you to give input that contains special characters, superscripts, built-up fractions, and so on.
The language incorporates many features of traditional mathematical notation. But you should realize that the goal of the language is to provide a precise and consistent way to specify computations. And as a result, it does not follow all of the somewhat haphazard details of traditional mathematical notation.
Nevertheless, as discussed in "Forms of Input and Output", it is always possible to get Mathematica to produce output that imitates every aspect of traditional mathematical notation. And it is also possible for Mathematica to import text that uses such notation, and to some extent to translate it into its own more precise language.