Variables in the C++ programming language, which Arduino uses, have a property called scope. This is in contrast to early versions of languages such as BASIC where every variable is a global variable.
There are two types of variables: global variable and local variable
- A local variable is the variable declared inside a function or a block of code (inside a curly brackets). The local variable only visible to the function or block of code in which they are declared.
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 own variables. This prevents programming errors when one function inadvertently modifies variables used by another function.