Doing Computations in Notebooks
A typical Mathematica
notebook containing text, graphics and Mathematica
expressions. The brackets on the right indicate the extent of each cell.
notebooks are structured interactive documents that are organized into a sequence of cells
. Each cell may contain text, graphics, sounds or Mathematica
expressions in any combination. When a notebook is displayed on the screen, the extent of each cell is indicated by a bracket on the right.
The notebook front end for Mathematica
provides many ways to enter and edit the material in a notebook. Some of these ways will be standard to whatever computer system or graphical interface you are using. Others are specific to Mathematica
|Shift||+||Enter||send a cell of input to the Mathematica kernel|
Doing a computation in a Mathematica notebook.
Once you have prepared the material in a cell, you can send it as input to the Mathematica
kernel simply by pressing Shift+Enter
. The kernel will send back whatever output is generated, and the front end will create new cells in your notebook to display this output. Note that if you have a numeric keypad on your keyboard, then you can use its Enter
key as an alternative to Shift+Enter
Here is a cell ready to be sent as input to the Mathematica
The output from the computation is inserted in a new cell.
Most kinds of output that you get in Mathematica
notebooks can readily be edited, just like input. Usually Mathematica
will convert the output cell into an input cell when you first start editing it.
Once you have done the editing you want, you can typically just press Shift+Enter
to send what you have created as input to the Mathematica
Here is a typical computation in a Mathematica
If you start editing the output cell, Mathematica
will automatically change it to an input cell.
After you have edited the output, you can send it back as further input to the Mathematica
When you do computations in a Mathematica
notebook, each line of input is typically labeled with In[n]:=
, while each line of output is labeled with the corresponding Out[n]=
There is no reason, however, that successive lines of input and output should necessarily appear one after the other in your notebook. Often, for example, you will want to go back to an earlier part of your notebook, and re-evaluate some input you gave before.
It is important to realize that in most cases wherever a particular expression appears in your notebook, it is the line number given in In[n]:=
which determines when the expression was processed by the Mathematica
kernel. Thus, for example, the fact that one expression may appear earlier than another in your notebook does not mean that it will have been evaluated first by the kernel. This will only be the case if it has a lower line number.
Each line of input and output is given a label when it is evaluated by the kernel. It is these labels, not the position of the expression in the notebook, that indicate the ordering of evaluation by the kernel.
The exception to this rule is when an output contains the formatted results of a Dynamic
function. Such outputs will re-evaluate in the kernel on an as-needed basis long after the evaluation which initially created them. See Dynamic Interactivity Language
for more information on this functionality.
As you type, Mathematica
applies syntax coloring to your input using its knowledge of the structure of functions. The coloring highlights unmatched brackets and quotes, undefined global symbols, local variables in functions and various programming errors. You can ask why Mathematica
colored your input by selecting it and using the item in the menu.
If you make a mistake and try to enter input that the Mathematica
kernel does not understand, then the front end will produce a beep and emphasize any syntax errors in the input with color. In general, you will get a beep whenever something goes wrong in the front end. You can find out the origin of the beep using the item in the menu.