What allows people to use a program on different operating systems

API (Application Programming Interface)

Explanation:

API in its simplest terms is just like a middle man that allows your computer run programs. Every computer has an operating system, some common operating systems include Windows, Linux, Mac and others. So when a program starts running on a computer, the computer's operating system understands or knows what to do through the API of the running program

to change your username, you must:

1) make sure what the username you want to change to is allowed in this community

2) contact a administrator (for example, jaysl)

3) through pm, tell the admin what you want to change to

4) if the username is allowed, it will be changed in a matter of seconds (minutes at most)

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