Differences between static keyword usage and dynamic variable

Why do I use static variables?

There are two ways to store variables: Static and Dynamic. dynamic variables are assigned storage units during program execution. When the program segment ends, these storage units are automatically released, static variables are stored in permanent storage units. The original storage unit is still used when the program segment is executed the next time.

Therefore, the life cycle of static variables will be extended until the end of the entire program running.
Test code:
# Include <stdio. h>
Void sum ();
Void main ()
{
Int a = 3;
Static int B;
Printf ("a = % d, B = % d \ n", a, B );
Sum ();
Sum ();
}
Void sum ()
{
Int a = 2;
Static int B = 10;
A + = 10;
B + = 20;
Printf ("a = % d, B = % d \ n", a, B );
}