Arduino - Scope

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## Variable Scope

Variables in the C programming language, which Arduino uses, have a property called scope. This is in contrast to languages such as BASIC where every variable is a global variable.

A global variable is one that can be seen by every function in a program. Local variables are only visible to the function in which they are declared. In the Arduino environment, any variable declared outside of a function (e.g. setup(), loop() ), is a global variable.

When programs start to get larger and more complex, local variables are a useful way to insure that only one function has access to its variables. This prevents programming errors when one function inadvertently modifies variables used by another function.

#### Example:

    int gPWMval;  // any function will see this variable

    void setup()
    {
      // ...
    }

    void loop()
    {
      int i;    // "i" is only "visible" inside of "loop"
      float f;  // "f" is only "visible" inside of "loop"
      // ...
    }

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