MacOS – How to enable automatic capitalization in OS X

I think the keyboard layout you are looking for is "ABC Extended" on Mac OS X El Capitan (10.11). If you are on an older version of Mac OS X this keyboard layout is called "US Extended", the rest of this answer uses the most recent name but everything else is the same between versions.

Here is how to enable either "ABC Extended" or "US International-PC".

In the Keyboard preference pane, click on the "plus" button in the lower left to add a new keyboard layout. Then select "English" in the next dialog box, scroll down to the bottom, select "ABC Extended" or whatever else you choose, and click "Add".

Here are the diacritical "dead keys" available in the standard US layout.

And here are the many more diacritical "dead keys" available in the ABC Extended layout, which provide for Eastern European and Slavic languages that use the Latin alphabet, along with other languages as well.

This screen shot shows the "option" keys in ABC Extended.

This screen shot shows the "shift-option" keys in ABC Extended.

Update

Here are other settings you need to be aware of.

Enable the pull-down menu on the menu bar. I would also un-check the box for "Automatically switch to a document's input source" because I find it too confusing in practice. But at least now you know where that setting is located.

It is also helpful to go to this pane and click the box to enable the Keyboard Viewer, so that you can see an on-screen floating window that shows you all the available diacritical dead keys in the layout that you have selected.

This is what the menu looks like (with whatever multiple layouts you wish to choose)

Here is where you can enable or disable the custom keyboard shortcuts to rotate among the list of different keyboard layouts which you have selected. I decided to disable these keyboard shortcuts because I found that it was too easy to accidentally rotate among multiple keyboard layouts and I was confusing myself as to which layout I was using at any given time. I would rather use the pull-down menu on the menu bar. It takes more time, but at least I am 100% sure of which keyboard layout I am using at any given moment.

In 10.9 the text replacements are also stored in ~/Library/Dictionaries/CoreDataUbiquitySupport/$USER~*/UserDictionary/local/store/UserDictionary.db. UserDictionary.db is used even if iCloud is disabled and it has precedence over .GlobalPreferences.plist.

If you for example run defaults write -g NSUserDictionaryReplacementItems '({on=1;replace=aa;with=bb;})' and quit and reopen TextEdit, aa is replaced with bb in TextEdit, but the changes are reverted if you open the Text tab of the Keyboard preference pane.

You can change both UserDictionary.db and .GlobalPreferences.plist by using a script like this:

date=$(date +%s)
while read -r replace with; do
  plist+="{on=1;replace=\"$replace\";with=\"$with\";},"
  sql+="INSERT INTO 'ZUSERDICTIONARYENTRY' VALUES($((++i)),1,1,0,0,0,0,$date,NULL,NULL,NULL,NULL,NULL,\"$with\",\"$replace\",NULL);"
done < <(sed 's/\\/\\\\/g;s/"/\\"/g' ~/replacements.txt)
sqlite3 ~/Library/Dictionaries/CoreDataUbiquitySupport/$USER~*/UserDictionary/local/store/UserDictionary.db "delete from ZUSERDICTIONARYENTRY;$sql"
defaults write -g NSUserDictionaryReplacementItems "(${plist%?})"

In 10.8 and earlier versions of OS X the text replacements are stored in the NSUserReplacementItems array (not NSUserDictionaryReplacementItems) in ~/Library/Preferences/.GlobalPreferences.plist.