#### 1.3.2.5 The `custom.i` file and `i-start/` directory ¶

When Yorick starts, the last thing it does before prompting you is to include the file `custom.i`. The default `custom.i` is in the `Y_SITE/i/custom.i`. (Yorick’s `help` command will tell you the actual name of the `Y_SITE` directory at your site.)

If you create the directory `~/yorick`, you can place your own version of `custom.i` there to override the default. Always begin by copying the default file to your directory. Then add your customizations to the bottom of the default file. Generally, these customizations consist of `#include` directives for function libraries you use heavily, plus commands like `pldefault` to set up your plotting style preferences.

Immediately before `custom.i`, yorick includes all files with the `.i` extension which are present in the `Y_SITE/i-start`, `Y_HOME/i-start`, and `~/yorick/i-start` directories. These files are intended to contain calls to the interpreted `autoload` function, which tells yorick what file to include in order to get the full definition of a function in some package not loaded by default. Using the `~/yorick/i-start`, you can autoload your own private functions, eliminating most of the reason for a `custom.i` file. See `Y_SITE/i-start` for examples of how to do this.