You can't actually input Alt codes on Macintosh. But there is even better alternative. You can use a standard built-in program. It's called "Keyboard viewer". It displays an on-screen keyboard with hell lots of characters.
Here are steps you need to accomplish to enable "Keyboard viewer" program on Mac computer.
- Choose Apple menu > System Preferences and click International.
- Click Input Menu, then select the check-box next to Keyboard Viewer.
- Select the "on" check-box next to language whose keyboard layout you want to use.
- Choose Show Keyboard Viewer from the Input menu on the right side of the menu bar (the one that looks like a flag).
Now, depending on the language you select, a flag will be in the menu bar. Whenever you want to type a special character, click the flag and select "Show Keyboard Viewer". When you press Shift and Option buttons, the on-screen keyboard will show up. And the good thing is, you don't have to keep a list of Alt codes near you.