学习C/C++同步进行第5课 Char\Short\Int\Long\Float\Double\LongDouble---hex\oct\dec

本文通过示例介绍了C/C++中不同数据类型占用的内存大小，包括char、short、int、long、long long、float、double和long double，并演示了如何进行十进制、十六进制和八进制之间的转换。同时，文章还讲解了浮点数的精度控制和符号常量的使用。

/*lesson 5*/
#include <iostream>
#include <string>

using namespace std;

#define PI 3.141
const float PAI = 3.141;

int main()
{
string type = "类型占用的字节数 = "; //字符串"类型"声明

   cout << "数据类型占用内存:" << endl;
   cout << "char"           << type << sizeof(char)           << endl;
   cout << "short"           << type << sizeof(short)       << endl;
   cout << "int"           << type << sizeof(int)           << endl;
   cout << "long"           << type << sizeof(long)           << endl;
   cout << "long long"       << type << sizeof(long long)   << endl;
   cout << "float"           << type << sizeof(float)       << endl;
   cout << "double"       << type << sizeof(double)       << endl;
   cout << "long double"   << type << sizeof(long double)   << endl;
   cout << endl;                                           //换行

   int A = 255;
   cout << "int类型举例:" << endl;
   cout << "默认十进制变量A = " << A << endl;
   cout << "十六进制输出 =" << hex << A << endl;
   cout << "八进制输出 =" << oct << A << endl;
   cout << "十进制输出 =" << dec << A << endl;
   cout << endl;                                           //换行

   char B = 'a';   char C = 97;
   cout << "char类型举例:" << endl;
   cout << "char B= 'a' B = " << B << endl;
   cout << "char C= 97 C = " << C << endl;
   cout << endl;                                           //换行

   float D = 12.3456789f;
   cout << "浮点数类型举例:(cout默认输出精度为6位数(整数+小数))" << endl;
   cout << "float D= 12.3456789 D = " << D << endl;
   cout << "修改输出精度为4位数(整数+小数)" << endl;
   cout.precision(4);//修改cout输出精度
   cout << "float D= 12.3456789 D = " << D << endl;
   cout << "添加定点法输出精度控制4位数,为小数点后面范围" << endl;
   cout.flags(cout.fixed);//定点法输出
   cout << "float D= 12.3456789 D = " << D << endl;
   cout << "取消定点法输出精度控制4位数,为整数+小数点后面范围" << endl;
   cout.unsetf(cout.fixed);//取消定点法输出
   cout << "float D= 12.3456789 D = " << D << endl;
   cout << endl;                                           //换行

   cout << "char 字面常量表示: 'a','b','X','-'... (字符上加单引号)" << endl;
   cout << "long 字面常量表示: 200L (后面加L)" << endl;
   cout << "long long 字面常量表示: 100000000000LL (后面加LL)" << endl;
   cout << "float 字面常量表示: 3.14f (后面加f)" << endl;
   cout << "double 字面常量表示: 3.0,3.14" << endl;
   cout << endl;                                           //换行

   cout << "符号常量代替字面常量 #define PI 3.141 PI = " << PI << endl;
   cout << "符号常量代替字面常量 const float PAI = 3.141; PAI = " << PAI << endl;
   cout << endl;                                           //换行

cout << endl; //换行
system("pause"); //程序暂停

return 0;
}

运行结果: