C++的数据类型

#include<iostream>
using namespace std;
int main1()
{
	//整型
	//1.短整型
	short num1 = 10;
	//short num1 = 32768;
	//2.整型
	int num2 = 10;
	//3.长整型
	long num3 = 10;
	//4.长长整型
	long long num4 = 10;
	cout << num1 << endl;
	cout << num2 << endl;
	cout << num3 << endl;
	cout << num4 << endl;
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
int main2()
{
	//整型：short(2) int(4) long(4) long long(8)
	//可以利用sizeof求出数据类型占用内存大小
	//语法：sizeof（数据类型/变量）
	short num1 = 10;
	cout << "short占用内存空间为：" << sizeof(short) << endl;
	//cout << "short占用内存空间为：" << sizeof(num1) << endl;
	int num2 = 10;
	cout << "int占用内存空间为：" << sizeof(int) << endl;
	//cout << "int占用内存空间为：" << sizeof(num2) << endl;
	long num3 = 10;
	cout << "long占用内存空间为：" << sizeof(long) << endl;
	//cout << "long占用内存空间为：" << sizeof(num3) << endl;
	long long num4 = 10;
	cout << "long long占用内存空间为：" << sizeof(long long) << endl;
	//cout << "long long占用内存空间为：" << sizeof(num4) << endl;
	//整型大小比较
	//short < int <= long <= long long
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
int main3()
{
	//实型
	//1.单精度 float
	//2.双精度 double
	//默认情况下，输出一个小数，会显示出6位有效数字
	float f1 = 3.1415926f;
	double d1 = 3.1415926;
	cout << "f1 = " << f1 << endl;
	cout << "d1 = " << d1 << endl;
	//float占用4字节内存空间，double占用8字节
	cout << "float占用的内存空间为：" << sizeof(float) << endl;
	cout << "double占用的内存空间为：" << sizeof(double) << endl;
	//科学计数法
	float f2 = 3e2; //3*10^2,300
	cout << "f2 = " << f2 << endl;
	float f3 = 3e-2; //3*0.1^2,0.03
	cout << "f3 = " << f3 << endl;
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
int main4()
{
	//1.字符型变量创建方式
	char ch = 'a';
	cout << ch << endl;
	//2.字符型变量所占内存大小
	cout << "char字符型变量所占内存为：" << sizeof(char) << endl;
	//3.字符型变量常见错误
	//char ch2 = "b"; 创建字符型变量时，要用单引号
	//char ch2 = 'abcdefg'; 创建字符型变量时，单引号内只能有一个字符
	//4.字符型变量对应ASCII编码
	//a - 97 A - 65
	cout << (int)ch << endl;
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
int main5()
{
	//转义字符
	//换行符\n
	cout << "Hello world" << endl;
	cout << "Hello world\n";
	//反斜杠\\
	cout << "\\" << endl;
	//水平制表符\t
	cout << "aaaa\thelloworld" << endl;
	cout << "aa\thelloworld" << endl;
	cout << "aaaaaa\thelloworld" << endl;
	system("pause");
	return 0;
}

#include<iostream>
#include<string> //用C++风格字符串时，要包含这个头文件
using namespace std;
int main6()
{
	//1.C风格字符串
	//注意事项1：char字符串名后加[]
	//注意事项2：等号后面要用双引号，包含起来字符串
	char str[] = "hello world";
	cout << str << endl;
	//2.C++风格字符串
	string str2 = "hello world";
	cout << str2 << endl;
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
int main7()
{
	//1.创建bool数据类型
	bool flag = true;
	cout << flag << endl;
	flag = false;
	cout << flag << endl;
	//1代表真，0代表假
	//2.查看bool类型所占内存空间
	cout << "bool类型所占内存空间：" << sizeof(bool) << endl;
	system("pause");
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
int main()
{
	//1.整型
	/*int a = 0;
	cout << "请给整型变量a赋值：" << endl;
	cin >> a;
	cout << "整型变量a = " << a << endl;*/
	//2.浮点型
	/*float f = 3.14f;
	cout << "请给浮点型变量f赋值：" << endl;
	cin >> f;
	cout << "浮点型变量f = " << f << endl;*/
	//3.字符型
	/*char ch = 'a';
	cout << "请给字符型变量ch赋值：" << endl;
	cin >> ch;
	cout << "字符型变量ch = " << ch << endl;*/
	//4.字符串型
	/*string str = "hello";
	cout << "请给字符串型变量str赋值：" << endl;
	cin >> str;
	cout << "字符串型变量str = " << str << endl;*/
	//5.布尔型
	bool flag = false;
	cout << "请给布尔型变量flag赋值：" << endl;
	cin >> flag;
	cout << "布尔型变量flag = " << flag << endl;
	system("pause");
	return 0;
}