If you've opened a text file and started editing it, then realize that you don't want to use the changes you've made, use the Revert command on the File Menu. When you select this command the dialog box shown in Figure 4.13 appears.

If you click the OK button, the last copy of the file you're working with will be opened, and all changes you have made since the last time you saved the file are lost. If you click Cancel, the file you're working with is not changed or saved to disk, and you can continue editing it.