本文学习自狄泰软件学院 唐佐林老师的 C++深度解析教程，图片全部来源于课程PPT，仅用于个人学习记录

第3课 - 进化后的 const 分析

实验-C与C++的const区别

#include <stdio.h>

int main()
{
    const int c = 0;
    int* p = (int*)&c;
    
    printf("Begin...\n");
    
    *p = 5;
    
    printf("c = %d,*p=%d\n", c,*p);
    
    printf("End...\n");
    
    return 0;
}
D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>gcc 31.c

D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>a
Begin...
c = 5,*p=5
End...

D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>g++ 31.cpp

D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>a
Begin...
c = 0,*p=5
End...

实验-C与C++的const区别&const作用域

#include <stdio.h>

void f()
{
    #define a 3
    const int b = 4;
}

void g()
{
//C++中，宏定义与const区别： define无作用域,const有作用域
    printf("a = %d\n", a);//预处理器直接将a替换为3
    //printf("b = %d\n", b);
    /*
    D:\Users\download\BaiDuDownload\test>g++ test.cpp
test.cpp: In function 'void g()':
test.cpp:12:24: error: 'b' was not declared in this scope
     printf("b = %d\n", b);
                        ^

*/
}

int main()
{
    const int A = 1;
    const int B = 2;
    int array[A + B] = {0};
    int i = 0;
    
    for(i=0; i<(A + B); i++)
    {
        printf("array[%d] = %d\n", i, array[i]);
    }
    
    f();
    g();
    
    return 0;
}

D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>gcc test.c
test.c: In function 'main':
test.c:19:5: error: variable-sized object may not be initialized
     int array[A + B] = {0};
     ^~~
test.c:19:25: warning: excess elements in array initializer
     int array[A + B] = {0};
                         ^
test.c:19:25: note: (near initialization for 'array')

D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>g++ test.cpp

D:\Users\download\BaiDuDownload\2 - C++深度解析教程\第1期 — 小试牛刀（免费）\test>a
array[0] = 0
array[1] = 0
array[2] = 0
a = 3

第4课 - 布尔类型和引用

#include <stdio.h>

int main(int argc, char *argv[])
{
    bool b = false;
    int a = b;
    
    printf("sizeof(b) = %d\n", sizeof(b));
    printf("b = %d, a = %d\n", b, a);
    
    b = 3;
    a = b;
    
    printf("b = %d, a = %d\n", b, a);
    
    b = -5;
    a = b;
    
    printf("b = %d, a = %d\n", b, a);
    
    a = 10;
    b = a;
    
    printf("a = %d, b = %d\n", a, b);
    
    a = 0;
    b = a;
    
    printf("a = %d, b = %d\n", a, b);
    
    return 0;
}
E:\test>g++ 4-1.cpp

E:\test>a
sizeof(b) = 1
b = 0, a = 0
b = 1, a = 1
b = 1, a = 1
a = 10, b = 1
a = 0, b = 0

E:\test>gcc 4-1.c
4-1.c: In function 'main':
4-1.c:5:5: error: unknown type name 'bool'; did you mean '_Bool'?
     bool b = false;

#include <stdio.h>

int main(int argc, char *argv[])
{
    int a = 4;
    int& b = a;
    
    b = 5;
    
    printf("a = %d\n", a);
    printf("b = %d\n", b);
    printf("&a = %p\n", &a);
    printf("&b = %p\n", &b);
    
    return 0;
}
E:\test>g++ 4-2.cpp

E:\test>a
a = 5
b = 5
&a = 000000000061FE14
&b = 000000000061FE14

小结