1.不能将一个数组赋值给另一个数组。
[cpp] view plain copy int a[5] = { 1, 2, 3, 4 }; char b[4] = { 'a' }; char c[10];//未初始化的字符好像经常会显示“烫烫烫烫烫”,哈哈哈哈哈哈哈哈哈哈哈 int d[4];//未初始化的int经常是-858993460。 百度一下： 烫烫烫和屯屯屯产生自VC，这是debug模式下VC对内存的初始化操作。 VC会把栈中新分配的内存初始化为0xcccccccc，而把堆中新分配的内存初始化为0xcd。 把0xcc和0xcd按照字符打印出来，就是烫和屯了。 还有锟斤拷，这个是字符编码造成的。在进行从老的编码体系到unicode的转换过程中， 部分字符不能转化，于是unicode给了它们一个特殊的占位符U + FFFD，这个用UTF - 8表示就成了\xef\xbf\xbd。 如果出现两个连着的\xef\xbf\xbd\xef\xbf\xbd，按照两个字节一个字显示成汉字，就成了锟斤拷这三个字。 而0xcccccccc用int格式就是-858993460了。。。 设计成0xcccccccc是有特殊用意的……这个好像叫做Poison，未初始化的Pointer去取值的话会出错。 肯定有人问为什么不弄成0x00000000，因为空指针是指针的有效状态，可能会误导人， 而0xCCCCCCCC在Windows下永远不可能是一个指针的有效状态（不是NULL，不指向一个对象，不指向一堆对象紧接之后的区域），这就是在模拟野指针
2.string是以\0结尾的，char[]没有特别赋值的话，是没有的。
[cpp] view plain copy char a2[5] = { 'a', 'b', 'c', 'd', 'e' }; char b2[5] = { 'a', 'b', 'c', 'd', '\0' }; cout << a2 << endl; cout << b2 << endl; cout的时候，a2是没有结尾的，所以会一直往下走，知道出现一个\0为止。
每一次运行的结果可能都不同。
3.C++对字符串的长度没有限制，处理的时候碰到\0就会结束。
4.字符串常量，隐式添加了\0。例如‘S’和“S”是不同的，“S”中实际是两个字符，S和\0。\0只会在末尾出现，两个字符串拼接，则中间是没有\0的。
5.通过cin输入的字符串，用空字符（空格、回车、制表符等）来结尾。
[cpp] view plain copy char a2[25] ; char b2[25] ; cout << "input name:" << endl; cin >> a2; cout << "input school" << endl; cin >> b2; cout << "name:" << a2 << endl; cout << "school:" << b2 << endl; 结果是：
输入的fable game之后，就跳过了。
这个数组超过25个之后居然还能正常输出。只不过后面就跟着中断了。
6.位字段，真惭愧，第一次听说到这个东西。每个字段占的内存是按位来算的，不是原来基础类型的字节大小。在成员名后面加个：和位数就可以了。
一般用于硬件编程了，已经非常非常底层了。怪不得还没听说过。
[cpp] view plain copy typedef struct bit_field { unsigned int a : 5; unsigned int b : 3; unsigned int c : 20; unsigned int d : 4; } bit_field_s;
7.共同体，用于节省内存。还是没有用过。。。。。。
8.枚举形的强制类型转换，好像是没有任何异常检测和抛错什么的。。。
[cpp] view plain copy enum EMyEnum { EMyEnum1, EMyEnum2, EMyEnum3, EMyEnum4, }; EMyEnum a = EMyEnum(5); 结果a的值是5. 这个平时写代码经常用到，自己写代码检测又嫌麻烦。只能自己把握了。
9.指针的声明，每一个变量都要带*
[cpp] view plain copy int i = 123; int* p1, p2; p1 = &i; p2 = &i;//这一句编译不过，因为p2是int，而不是int*
10.new分配的内存一般都在堆（heap）或者自由存储区中，变量声明的内存一般都在栈（stack）中。
11.C++3中管理内存的方式：自动存储，静态存储，动态存储。
a.自动存储：局部变量，放在栈中，后进先出。函数被退出栈，变量就没了。
b.静态存储：static，或者写在函数外
c.动态存储：new出来的都是，放在堆中。
[cpp] view plain copy #include "Chapter4.h" #include <iostream> #include "Chapter2.h" using namespace std; class CTest { public: CTest(char c); ~CTest(); static CTest* getACTest(); private: char flag; }; CTest::CTest(char c) { flag = c; cout << "create CTest, flag:" << flag << endl; } CTest::~CTest() { cout << "delete CTest, flag:" << flag << endl; } CTest* CTest::getACTest() { CTest b('b'); CTest* c = new CTest('c'); return c; } static CTest a('a'); void CChapter4Answer::answer() { CTest* c = CTest::getACTest(); CTest d('d'); } 试了一下，各个地方的变量什么时候创建和删除。
最后得到的结果：
因为a是静态变量，所以程序启动的时候先创建了a，然后才进入main函数。
在getTest函数内先创建了b，然后new了一个c。b是声明出来的，所以函数结束之后，就会删除掉，而c是new出来的，放在堆中。
然后创建d，删除d，其实d就是在一个更大的函数内而已。
然后走完main函数，在外面才删除了a。静态变量是在关闭程序的时候才回收的。
然后c呢，c的析构函数没有走到。证明在堆中的内存，程序是不会回收的，这就是内存泄露了吧。相信操作系统会回收吧。
另外，走出了main函数之后，还是有别的操作的。这真是第一次知道。
要人工确保new和delete，对于稍微大一点的程序来说，应该不大可能吧。一般都会用智能指针，所以我在工作中，根本没有主动使用过delete这个关键字。
但是即使是智能指针，还是会出现内存泄露的情况。最先想到的就是两个智能指针互相指向，都在等对方释放。
12.vector初始化可以用{}直接包含一些元素进去。
[cpp] view plain copy CTest* c = CTest::getACTest(); CTest d('d'); vector<CTest> e = { d };//这个很方便
4.12 复习题
[cpp] view plain copy //1 char actor[30] = { 0 }; short betsie[100] = { 0 }; float chuck[13] = { 0 }; long double dipsea[64] = { 0 };
[cpp] view plain copy //2 array<char, 30> actor = { 0 }; array<short, 100> betsie = { 0 }; array<float, 13> chuck = { 0 }; array<long double, 64> dipsea = { 0 };
[cpp] view plain copy //3 int a[5] = { 1, 2, 3, 4, 5 };
[cpp] view plain copy //4 int even = a[0] + a[4];
[cpp] view plain copy //5 float ideas[5] = { 1, 2, 3, 4, 5 }; cout << "ideas[1]:" << ideas[1] << endl;
[cpp] view plain copy //6 char c[20] = "cheeseburger"; cout << c << endl; [cpp] view plain copy //7 string str = "Waldorf Salad"; cout << str << endl;
[cpp] view plain copy //8 struct SFish { char type[20]; int weight; double lenght; };
[cpp] view plain copy //9 SFish fish = { "big", 2, 3.4 }; 1.
[cpp] view plain copy //10 enum Response { No, Yes, Maybe, };
[cpp] view plain copy //11. double ted = 123.456; double* tedPtr = &ted; cout << *tedPtr << endl;
[cpp] view plain copy //12. float treacle[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; float* ptr = treacle; cout << ptr[0] << " " << ptr[9] << endl;
[cpp] view plain copy //13 int n = 0; cin >> n; int* a = new int[n]; vector<int> b(n); for (int i = 0; i < n; i++) { a[i] = i;//原来调试的时候，是看不到a指向的数组的内存的。 b[i] = i; } for (int i = 0; i < n; i++) { cout << a[i] << " " << b[i] << endl; }
[cpp] view plain copy /*14.语句没有问题。其实就是把字符串指针，强制转换成整形指针。 cout只对字符串指针进行特殊处理，其他类型的指针是输出该指针的内容，即地址。*/ char* b = "Home of the jolly bytes"; int* a = (int *)b; cout << a << " " << *a << endl; cout << b << " " << *b << endl; cout << (int *)"Home of the jolly bytes" << endl;
[cpp] view plain copy //15. struct SFish { char type[20]; int weight; double lenght; }; SFish* fish = new SFish{ "big", 2, 3.4 }; cout << "fish type:" << fish->type << " wight:" << fish->weight << " lenght:" << fish->lenght << endl;
[cpp] view plain copy //16.还是要看看4.6清单的代码 只读单词，不能读整行 int year; cin >> year;//这里点了回车键 char address[80]; cin.getline(address, 80);//这里只读了一个回车键，没机会输入 cout << year << " " << address << endl;//address没有相应的内容 cin >> year; cin >> address; cout << year << " " << address << endl;//可以输入adress，不能读取空白字符，只能读一个单词
[cpp] view plain copy //17. const int num = 10; vector<string> a(num);// #include <string> array<string, num> b;// #include <array>
4.13 编程练习
[cpp] view plain copy //1 string firstName = ""; string lastName = ""; cout << "What is your first name? " ; getline(cin, firstName); cout << "What is your last name? "; getline(cin, lastName); cout << "What letter grade do you deserve? "; char grade; cin >> grade; grade++; cout << "What is your age?"; int age; cin >> age; cout << "Name: " << lastName << ", " << firstName << endl; cout << "Grade: " << grade << endl; cout << "Age: " << age << endl;
[cpp] view plain copy //2 string name; string dessert; cout << "Enter your name:\n"; getline(cin, name); cout << "Enter your favorite dessert:\n"; getline(cin, dessert); cout << "I have some delicious " << dessert; cout << " for you, " << name << endl;
[cpp] view plain copy //3 cout << "Enter your first name:"; char firstName[20]; cin.getline(firstName, 20); cout << "Enter your last name:"; char lastName[20]; cin.getline(lastName, 20); char name[80] = {0};//这个不初始化会出现中断 strcat_s(name, firstName); strcat_s(name, ", "); strcat_s(name, lastName); cout << "Here's the information in a single string: "<< name;
[cpp] view plain co //4 string firstName = ""; string lastName = ""; cout << "Enter your first name:"; getline(cin, firstName); cout << "Enter your last name:"; getline(cin, lastName); string name = firstName + ", " + lastName; cout << "Here's the information in a single string: " << name;
[cpp] view plain copy //5 struct CandyBar { string brand;//品牌 double weight;//重量 int calorie;//卡路里 }; CandyBar snack = { "Mocha Munch", 2.3, 350 }; cout << "Candy brand:" << snack.brand << " weight:" << snack.weight << " calorie:" << snack.calorie;
[cpp] view plain copy //6 struct CandyBar { string brand;//品牌 double weight;//重量 int calorie;//卡路里 void getInfo() { cout << "Candy brand:" << brand << " weight:" << weight << " calorie:" << calorie << "\n"; } }; CandyBar snack = { "Mocha Munch", 2.3, 350 }; snack.getInfo(); CandyBar candyArr[3] = { { "Mocha Munch", 2.3, 350 }, { "Big Rabbit", 3.4, 150 }, { "Alps", 4.5, 650 } }; candyArr[0].getInfo(); candyArr[1].getInfo(); candyArr[2].getInfo(); [cpp] view plain copy //6 struct Pizza { string company;//品牌 double weight;//重量 double diameter;//直径 }; Pizza p = { "", 0, 0 }; cout << "Please enter company:"; getline(cin, p.company); cout << "Please enter diameter:"; cin >> p.diameter; cout << "Please enter weight:"; cin >> p.weight; cout << "Pizza company:" << p.company << "\ndiameter:" << p.diameter << "\nweight:" << p.weight << "\n";
[cpp] view plain copy //7 struct Pizza { string company;//品牌 double weight;//重量 double diameter;//直径 }; Pizza* p = new Pizza{ "", 0, 0 }; cout << "Please enter diameter:"; cin >> p->diameter; getline(cin, p->company);//把回车符读取了 cout << "Please enter company:"; getline(cin, p->company); cout << "Please enter weight:"; cin >> p->weight; cout << "Pizza company:" << p->company << "\ndiameter:" << p->diameter << "\nweight:" << p->weight << "\n"; delete p; p = NULL;
[cpp] view plain copy //9 struct CandyBar { string brand;//品牌 double weight;//重量 int calorie;//卡路里 void printInfo() { cout << "Candy brand:" << brand << " weight:" << weight << " calorie:" << calorie << "\n"; } }; CandyBar* candyArr = new CandyBar[3]; candyArr[0] = { "Mocha Munch", 2.3, 350 }; candyArr[1] = { "Big Rabbit", 3.4, 150 }; candyArr[2] = { "Alps", 4.5, 650 } ; candyArr[0].printInfo(); candyArr[1].printInfo(); candyArr[2].printInfo(); delete[] candyArr; candyArr = NULL;
[cpp] view plain copy //10 array<double, 3> socreArr; cout << "Please enter you score:"; cin >> socreArr[0]; cout << "Please enter you score:"; cin >> socreArr[1]; cout << "Please enter you score:"; cin >> socreArr[2]; double totalScore = socreArr[0] + socreArr[1] + socreArr[2]; cout << "times:" << 3 << " averageScore:" << totalScore/3;
