C++ Tutorial/Language Basics/global variable — различия между версиями
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Текущая версия на 10:30, 25 мая 2010
Содержание
Global class variable
#include<iostream.h>
class test
{
int i;
public:
test()
{
i=25;
for(int ctr=0; ctr<10;ctr++)
{
cout<<"Counting at"<<ctr<<"\n";
}
}
~test(){};
};
test anObject;
main()
{
return 0;
}Counting at0 Counting at1 Counting at2 Counting at3 Counting at4 Counting at5 Counting at6 Counting at7 Counting at8 Counting at9
Global variables are known throughout the entire program and may be used by any piece of code.
#include <stdio.h>
void func1(void), func2(void);
int count;
main(void)
{
count = 100;
func1();
return 0;
}
void func1(void)
{
int temp;
temp = count;
func2();
printf("count is %d", count); /* will print 100 */
}
void func2(void)
{
int count;
for(count=1; count<10; count++)
putchar(".");
}Use a global variable
#include <iostream>
using namespace std;
void func1();
void func2();
int count; // This is a global variable.
int main()
{
int i; // This is a local variable
for(i=0; i<10; i++) {
::count = i * 2;
func1();
}
return 0;
}
void func1()
{
cout << "count: " << ::count; // access global count
cout << "\n";
func2();
}
void func2()
{
int count;
for(count=0; count<3; count++)
cout << ".";
}count: 0 ...count: 2 ...count: 4 ...count: 6 ...count: 8 ...count: 10 ...count: 12 ...count: 14 ...count: 16 ...count: 18 ...
Use :: to reference global variable
#include <iostream>
using namespace std;
int global_name = 1001;
int main(void){
int global_name = 1; // Local variable
cout << "Local variable value " << global_name << "\n";
cout << "Global variable value " << ::global_name << "\n";
}