No extern keyword in Java.
The CTRL key is the only difference. What it actually does depends on the currently active program and/or control, and whether or not the key combo has been implemented or not. If not, the shell processes the key combo. On my system (Windows 7), both combos bring up the task switcher.
An allen key is a square key normally used for a square headed bolt or screw used in mainly self build furniture (flat packed).
Of course they are used. Both stand-alone and class-member functions are used in C++.
The goto statement.