c ++查找字符串

Program 1:

程序1：

#include <iostream>
#pragma pack(1)
using namespace std;
typedef struct{
int A;
int B;
char c1;
char c2;
} S;
int main()
{
cout << sizeof(S);
return 0;
}

Output:

输出：

In a 32-bit system: 10
In a 64-bit system: 18

Explanation:

说明：

We compiled the program on a 32-bit system. It will print "10" on the console screen.

我们在32位系统上编译了该程序。 它将在控制台屏幕上打印“ 10” 。

Normally, the above program will print "12" due to structure padding. But, here, we used #pragma pack(1) directives. It is used to avoid the structure padding. Then the size of the above structure will be "10".

通常，由于结构填充，上述程序将打印“ 12” 。 但是，在这里，我们使用了#pragma pack(1)指令。 用于避免结构填充。 那么上述结构的大小将为“ 10” 。

Program 2:

程式2：

#include <iostream>
using namespace std;
struct st {
char c1;
int A;
int B;
char c2;
};
int main()
{
struct st* ptr;
cout << sizeof(ptr);
return 0;
}

Output:

输出：

In a 32-bit system: 4
In a 64-bit system: 8

Explanation:

说明：

We compiled this program on a 32-bit system.

我们在32位系统上编译了该程序。

Here, we created a structure with 4 members, and a pointer to the structure.

在这里，我们创建了一个具有4个成员的结构 ，以及一个指向该结构的指针。

cout<<sizeof(ptr);

The above statement will print "4". Because, the size of any type of pointer in a 32-bit system is 4 bytes.

上面的语句将打印“ 4 ”。 因为，在32位系统中，任何类型的指针的大小均为4个字节。

Program 3:

程式3：

#include <iostream>
using namespace std;
struct st {
char c1;
int A;
int B;
char c2;
};
int main()
{
struct st ob;
struct st* ptr = &ob;
cout << sizeof(*ptr);
return 0;
}

Output:

输出：

16

Explanation:

说明：

We compiled the program on 32-bit based system.

我们在基于32位的系统上编译了该程序。

Here, we created a structure, C++ uses structure padding and allocate space for variables block-wise, block size is 4 bytes for 32-bit based system.

在这里，我们创建了一个结构，C ++使用结构填充并按块逐个分配变量，对于基于32位的系统，块大小为4个字节。

In the main() function we created a structure variable ob, and a pointer ptr that contains the address of ob.

在main()函数，我们创建了一个结构变量的ob和包含OB的地址的指针PTR。

cout<<sizeof(*ptr);

The above statement will print the size of the structure.

上面的语句将打印结构的大小。

1st block is allocated for c1 that is 4 bytes.
2nd block is allocated for A that is 4 bytes.
3rd block is allocated for B that is 4 bytes.
4th block is allocated for c2 that is 4 bytes.

Then, the total size is "16" bytes will be printed on the console screen.

然后，总大小为“ 16”字节将被打印在控制台屏幕上。

翻译自: https://www.includehelp.com/cpp-tutorial/structures-find-output-programs-set-3.aspx

c ++查找字符串