C++数据处理

                //
                cout<<hex;和cout<<oct;控制符实际上是一条消息，告诉cout采取何种行为
#include<iostream>
usingnamespace std;
int main()
{
    usingnamespace std;
    int chest =42;
    int waist =42;
    int inseam=42;

    cout<<"Monsieur cuts a striking figure!"<<endl;
    cout<<"chest= "<<chest<<" (decimal)"<<endl;
    cout<<hex;//不会再屏幕上显示任何内容，而只是显示cout显示整数的方式
    cout<<"waist= "<<waist<<" hexadecimal"<<endl;
    cout<<oct;
    cout<<"inseram= "<<inseam<<" (octal)"<<endl;
    return0;
}

/shortintlong 
#include<iostream>
#include<limits.h>
int main()
{
    usingnamespace std;
    int n_int=INT_MAX;
    short n_short=SHRT_MAX;
    long n_long=LONG_MAX;

    cout<<"int is "<<sizeof(int)<<" bytes."<<endl;
    cout<<"short is "<<sizeof n_short<<" bytes."<<endl;
    cout<<"long is "<< sizeof n_long<<" bytes."<<endl;

    cout<<"Maximum values:"<<endl;
    cout<<"int: "<<n_int<<endl;
    cout<<"short: "<<n_short<<endl;
    cout<<"long: "<<n_long<<endl;

    cout<<"Minimum int value= "<<INT_MIN<<endl;
    cout<<"Bits per byte= "<<CHAR_BIT<<endl;
    return0;
}

                无符号数
/如何使用无符号类型，程序试图超越整型的限制时将产生的结果
//这些整型变量的行为就像里程表，一旦超出了限制，其值将为范围另一端的取值
#include<iostream>
#define ZERO 0
#include<climits>
int main()
{
    usingnamespace std;
    short sam=SHRT_MAX;
    unsigned short sue=sam;

    cout<<"Sam has "<<sam<<" dollars and sue has "<<sue<<" dollars deposited."<<endl;
    cout<<"Add $1 to each account."<<endl<<"Now ";
    sam=sam+1;
    sue=sue+1;
    cout<<"Sam has "<<sam<<" dollars and sue has "<<sue<<" dollars deposited."<<endl;
    sam=ZERO;
    sue=ZERO;
    cout<<"Sam has "<<sam<<" dollars and sue has "<<sue<<" dollars deposited."<<endl;
    sam=sam-1;
    sue=sue-1;
    cout<<"Sam has "<<sam<<" dollars and sue has "<<sue<<" dollars deposited."<<endl;
    cout<<"Lucky sue!"<<endl;
    return0;
}

                //
                值的类型引导cout选择如何显示值

                //
                ch实际上是一个整数，因此可以对它使用整数操作
#include<iostream>
int main()
{
    usingnamespace std;
    char ch=‘M‘;
    int i=ch;
    cout<<"The ASCII code for  "<<ch<<" is "<<i<<endl;

    cout<<"Add one to the character code:"<<endl;
    ch=ch+1;//对ch使用整数操作
    i=ch;
    cout<<"The ASCII code for  "<<ch<<" is "<<i<<endl;
    cout<<"Displaying char ch using cout.put(ch):";
    cout.put(ch);//成员函数调用   通过类对象cout来使用函数put()
    cout.put(‘!‘);
    cout<<endl<<"Done!"<<endl;
    return0;
}

//cout<<‘$‘;//打印$的ASCII值
//cout.put(‘$‘);//打印字符$

                float和double类型精度差异

                //
                float和double类型及它们表示数字时在精度方面的差异

                //
                float确保至少有6位有效位，double确保至少有15位有效位

                //
                浮点常量默认为double类型
#include<iostream>
int main()
{
    usingnamespace std;
    cout.setf(ios_base::fixed,ios_base::floatfield);
    float tub=10.0/3.0;
    double mint=10.0/3.0;
    constfloat million=1.0e6;

    cout<<"tub= "<<tub;
    cout<<",a milloin tubs= "<<million*tub;
    cout<<",\n and ten million tubs = "<<10*million*tub<<endl;

    cout<<"mint= "<<mint<<" and a million mints = "<<million*mint<<endl;
    return0;
}

                浮点数的优缺点

                //
                浮点数的优缺点

                //
                1.可以表示整数之间的值。2.有缩放因子所以表示值的范围更大

                //
                a、运算速度比整数慢。b、精度降低
#include<iostream>
int main()
{
    usingnamespace std;
    float a=2.34e+22f;
    float b=a+1.0f;

    cout<<"a= "<<a<<endl;
    cout<<"b-a= "<<b-a<<endl;
    return0;
}

//程序运行结果b-a的值等于0.  问题在于a的值是一个小数点左边有23位的数字。加上1就是在第23位加1
//但float类型只能表示数字中的前6位或前7位，因此修改第23位对这个数的值不会有影响。

                //
                c++中的/运算

                //
                在对不同类型进行运算时，把它们转换为同一类型
#include<iostream>
int main()
{
    usingnamespace std;
    cout.setf(ios_base::fixed,ios_base::floatfield);
    cout<<"Integer  division:9/5= "<<9/5<<endl;
    cout<<"Floating-point division:9.0/5.0= "<<9.0/5.0<<endl;
    cout<<"Mixed division: 9.0/5= "<<9.0/5<<endl;
    cout<<"double constants:1E7/9.0= "<<1e7/9.0<<endl;
    cout<<"float constants:1e7f/9.0f= "<<1e7f/9.0f<<endl;
    return0;
}

                //
                强制类型转换
#include<iostream>
int main()
{
    usingnamespace std;
    int duks,bats,coots;

    duks=19.99+11.99;                //31.98赋给变量duks时，被截短为31
    bats=(int)19.99+(int)11.99;        //在进行加法运算之前先被截断为19和11，所以变量的值为30
    coots=int(19.99)+int(11.99);

    cout<<"duks= "<<duks<<",bats= "<<bats<<",coots= "<<coots<<endl;
    char ch=‘Z‘;
    cout<<"The code for "<<ch<<" is "<<int(ch)<<endl;//利用强制转换打印字符对应的整数。return0;
}