C++ 数据处理(二)---进制、数据类型

//符号常量

#include<climits>

short s = SHRT_MAX;    int a = INT_MAX;    char c = CHAR_MAX;    cout << sizeof(a) << endl << sizeof(float)  << endl << sizeof(c) <<endl << sizeof(s) << endl;

//C++赋值语法

int bb(100);    int bbb(0);    int bbbb = (11);        int cc = {200}; //200    int ccc = {0};   // 0    int cccc{11};

//C++进制转换

int d = 200;   //200   10进制    int dd = 200;  //0xc8  16进制 头两位0x或者0X 其它a~F 0~9    int ddd = 200; //0310  8进制 第一位0  其它1~7        cout << "输出十进制值"  << endl << d <<endl;  //默认cout的输出是十进制，也可以显式加标识符    cout << "输出十进制值"  << endl  << dec << d <<endl;    cout << "输出十六进制值"  << endl  << hex << dd <<endl;        cout << "输出八进制值"  << endl  << oct << ddd <<endl;

输出十进制值

200

输出十进制值

200

输出十六进制值

c8

输出八进制值

310

//C++ 数组语法,省略等号

const int code = 10;    char cc[] {'a','y'};    char *q = "sdsdf";    char qq = 'a';    char qqq[] = "sdfsdf";    char qqqq[] = {'q','q'};    char *qqqqq[] = {"sdf"};

//自动数据类型 auto (比较少普及)

auto a_c = 'a'; //char    auto a_f = 1.0; //float    auto a_i = 1;  //int        size_t s_a_c = sizeof(a_c);  //1字节    size_t s_a_f = sizeof(a_f);  //8字节    size_t s_a_i = sizeof(a_i);  //4字节

//关键字类型 decltype

float x = 10.0f;    float &d = x;    decltype(x) y;         // y type float    decltype(buy(20)) yy;  // yy type buy return int    decltype(d) yyy = x;   // yyy type float &    decltype(d+d) y4;      // y4 type float

//强转

char t = 88;    char t2 = 'X';    int a = (int)t;    a = (int)t2;    cout << t << endl << t2 << endl;