This appendix summarizes MATLAB commands and functions that are especially useful to the study of signals and systems and that have been used throughout the text. A number of these functions are specific to some optional MATLAB toolbox;^{1} all the commands used here may be found in the MATLAB *Student Version*. MATLAB is a rich and powerful tool that boasts many more commands and options than can be listed here. For more advanced use of system tools, the MATLAB documentation or help screens should be referenced.

Using only the commands found here, a variety of signals can be defined and plotted, a system can be defined in one of several ways, the system behavior can be confirmed, and a test signal can be input to the system to observe the output. Each of these operations can be readily accomplished in a few lines.

`% MATLAB comments are text like this after a percent sign.`

Variable names in MATLAB are *case sensitive*, such that Power is different from power.

A few mathematical constants are predefined in MATLAB, including:

```
i % = square root of -1
j % = square root of -1
pi % = 3.14159 ···
```

These predefined values may be overwritten or redefined, and care should taken to not use these variable names in other contexts. The default value of any of the above constants can be restored using the command clear. For example: ...

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