Outside the Function...
1000 2000
Inside the Function...
1000 2000
100 200
After the change: 1500 2000
Outside the Function...
1500 2000
100
After the change: 150
 
    Variables defined outside of the function are global for read only.
    If you need to update those variable within a function, you must declare those as global.
    Variables defined inside a function cannot be accessed from outside, unless declared as global.