#include
#include
#include
int main()
{
int ret = 0;
int i = 0;
for( i = 0; i < 2; i++ )
{
fork();
printf( "a\n" );
}
return ret;
}
#include
#include
using namespace std;
class A
{
public:
int &b;
int a;
};
int main()
{
int ret = 0;
cout << sizeof(int*) << " " << sizeof(A) << " " << sizeof(int) << endl;
unsigned int a = 0x1FFFFFF7;
unsigned char b = a;
char c = a;
char *p = ( char * )&a;
long long data = 0xf1f2f3f4f8f0f5f7;
cout << sizeof(long long) << endl;
printf( "%x, %x, %x, %x\n", b, c, *p, data );
long long a1 = 1, b1 = 2, c1 = 3;
printf( "%d, %d, %d\n", a1, b1, c1 );
return ret;
}
1. #define定义的宏只在本文件有效
#ifndef MYFILE
#define MYFILE
void test();
#endif
#include
using namespace std;
#define MAX 10
void func()
{
#ifdef MYFILE
cout << "MYFILE is defined" << endl;
#else
cout << "MYFILE is not defined" << endl;
#endif
return;
}
#include "myheader.h"
#include
using namespace std;
extern void func();
int main()
{
func();
return 0;
}
g++ use1.cpp use2.cpp -o use
./use
MYFILE is not defined
故下面代码是为了防止同一个文件包含一个头文件多次
#ifndef MYFILE
#define MYFILE
#endif
===========================
#include
using namespace std;
int cnt = 0;
int show()
{
cnt = 9;
return 0;
}
int main()
{
cout << show() << ', ' << cnt << endl;
return 0;
}
#include "myheader.h"
#include
using namespace std;
extern void func();
extern const int v1;
extern const int v2;
class Test
{
private:
static int a;
};
int Test::a = 10;
void f( const int &a )
{
cout << "test f(const int&)" << endl;
return;
}
int mal( int a, int b = 2, int c = 4 )
{
cout << a + b + c << endl;
return 0;
}
template <typename T> T add( T x, T y )
{
return x + y;
}
class A
{
public:
int a;
int &b;
};
void prim( int m, int n )
{
if( m >= n )
{
while( m % n != 0 )
{
++n;
}
cout << n << endl;
m /= n;
prim( m, n );
}
return;
}
typedef int* PINT;
typedef int *PINT1;
typedef int fun( int *, int );
int testfun( int *p, int a )
{
return a;
}
class ConstRef
{
public:
ConstRef( int ii ) : i(ii), ci(i), ri(ii){}
void show()
{
cout << ci << ' ' << ri << endl;
ri = 8;
cout << ci << ' ' << ri << endl;
}
private:
int i;
const int ci;
int &ri;
};
int main()
{
int hah = 0;
int &p33 = hah;
cout << sizeof(int) << ' ' << sizeof(const int) << ' ' << sizeof(p33) << endl;
cout << sizeof(ConstRef) << endl;
ConstRef obj(3);
obj.show();
int t1 = 9;
const PINT p = &t1;
const int *p2 = &t1;
const PINT1 p3 = &t1;
*p3 = 3;
*p = 10;
cout << t1 << endl;
int *p1;
int data = 27;
while( cin >> data )
{
prim( data, 2 );
cout << "===============================" << endl;
}
cout << "sizeof(A)=" << sizeof(A) << endl;
cout << "sizeof(int) = " << sizeof(int) << endl;
add<float>( 4.3, 3 );
func();
cout << v2 << endl;
const char *pp;
cout << mal( 2 ) << endl;
f(1);
return 0;
}
#include
using namespace std;
#define MAX 10
const int v1 = 10;
extern const int v2 = 20;
void func()
{
#ifdef MYFILE
cout << "MYFILE is defined" << endl;
#else
cout << "MYFILE is not defined" << endl;
#endif
return;
}