You can download the 15 free lessons from here on a PDF file.
This is a free lesson from The Computer Manual, if you are interested in a computer basics manual, and or tutorials, visit the TheComputerManual.com to see the contents and pricing of the book and the video tutorials.
The undo command is very useful too. Every time when you work on any type of project just use undo if you don’t like the last changes you did. The shortcut key is “Ctrl+Z”. But you can also use the Redo command to redo the changes. “Ctrl+Y”
The Undo and Redo commands work throughout all applications you might use, sometimes applications tend to change the shortcut key used for Undo or Redo.