objective-C global static variables

#include <stdio.h>
#include <stdlib.h>

// Declare a global variable
float lastTemperature;

Global variables are available to the code in every one of those files. Sometimes sharing a variable between different files is what you want. But, as you can imagine, having a variable that can be accessed by multiple functions can also lead to great confusion. To deal with this, we havestatic variables. 

// Declare a static variable
static float lastTemperature;

A static variable is like a global variable in that it is declared outside of any function. However, a static variable is only accessible from the code in the file where it was declared. So you get the non-local, “exists outside of any function” benefit while avoiding the “you touched my variable!” issue.