0 Undo and Redo

The "Undo" and "Redo" commands.

Until now we have seen some drawing and editing commands, will often have to undo the last operations performed, especially the editing operations such as scale, stretch, etc..
In these cases we use the 'Undo' command , Which is on the standard toolbar.
Each time you press this key, Autocad undo the operations performed in sequence on the drawing of any kind they are.

In practice Autocad save all transactions made by the time we open a drawing, or do when we create a new one, all these operations can be canceled from the last, back to start.

In the opposite way with the 'Redo'  you can restore any operations that you previous canceled by pressing 'Undo' command .

A situation where it can be useful this command is as follows:
Suppose you open an existing drawing that you have to change, while retaining a copy of the current version.
After performing some changes, instead of saving the file with another name, click "Save" by mistake. 
At this point the file is saved with the new changes and the old version is lost.

To retrieve just save the drawing with another name (so we will have two identical copies of the amended design), then we will use several times the command "Undo" to go back with the changes made until we started to change design.

Now just repeat a "save as" and overwrite the first source file, so we will have recovered by undoing changes to the original back, but we will also have the new file with the changes made, previously saved.