Day12

继续看范例fig06_12.cpp下半段，一开始定义三个函式原型void useLocal(), void useStaticLocal(), void useGlobal(), 我稍微修改了一下main(),透过for回圈各自呼叫三次，可以发现useStaticLocal()与useGlobal()的变数x的值各累加了两次，但 useLocal()里x的值并没有改变。

• Result

local x is 100
local static x is 200
global x is 300

local x is 100
local static x is 201
global x is 301

local x is 100
local static x is 202
global x is 302

• fig06_12.cpp

#include <iostream>
using std::cout;
using std::endl;

void useLocal(); // function prototype
void useStaticLocal(); // function prototype
void useGlobal(); // function prototype

int x = 300; // global variable

int main()
{
   for (int i = 0; i <3; i++)
   {
      useLocal(); // useLocal has local x
      useStaticLocal(); // useStaticLocal has static local x
      useGlobal(); // global x also retains its value
      cout << endl;
   }

   return 0; // indicates successful termination
} // end main

// useLocal reinitializes local variable x during each call
void useLocal( void )
{
   int x = 100; // initialized each time useLocal is called
   
   cout << "\nlocal x is " << x ;
   x++;
} 

void useStaticLocal( void )
{
   static int x = 200; // initialized first time useStaticLocal is called 

   cout << "\nlocal static x is " << x ;
   x++; 
} 

void useGlobal( void )
{
   cout << "\nglobal x is " << x ;
   x++; 
}