Hour 13. Adding Undo and Redo Functionality

The first computers were considered unfriendly and hard to use because they were unforgiving of user error. You said you wanted to erase your hard drive? OK! I’m busy now; don’t interrupt me! Users avoided exploring their application’s user interfaces for fear of breaking something irreversibly. The result was that most software features were never used. Undo/redo is the unsung hero that led computers to be widely adopted. Although the Xerox Alto, the first computer to provide a GUI, introduced undo functionality in 1973, it took a long time to be widely adopted, partially because programmers did not know ...

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