How the computer handles variables

static_variable.c

#include <stdio.h>

void addValue() {
  // It doesn't reset every time I call.
  static int a = 10;
  a = a + 10;
  printf("%d\n", a);
}

int main(void) {
  addValue()
  addValue()
  addValue()
  addValue()
  // a = 50
  
  system("pause");
  return 0;
}