C++文件的存取

实例：

#include <iostream>
#include <fstream>
using namespace std;

double CalculateTax(double);

int main()
{
char* FileNameIn = "Income.txt";
char* FileNameOut = "Tax.txt";
double Income, Tax;

ifstream FileInput;//定义了名为FileInpu的输入型文件数据流
ofstream FileOutput;//定义了名为FileOutput的输出型文件数据流
FileInput.open(FileNameIn);
FileOutput.open(FileNameOut);

if (!FileInput)
{
cout << "文件:" << FileNameIn
<< "打开失败！" << endl;
exit(1);//要求操作系统立即中止此程序的执行
}

if (!FileOutput)
{
cout << "文件：" << FileNameOut
<< "存档失败！" << endl;
exit(1);
}

FileInput >> Income;
Tax = CalculateTax(Income);
cout << "要缴纳的综合所得税："
<< Tax << "元\n";
FileOutput << "要缴纳的综合所得税："
<< Tax<<"元\n";
FileInput.close();//关闭输入文件
FileOutput.close();//关闭输出文件
return 0;
}

double CalculateTax(double GIncome)
{
double Tax;
if (GIncome<0.0)
{
cout << "没有意义！\n";
}
else if (GIncome<330000.0)
{
Tax = GIncome*0.06;
}
else if (GIncome < 890000.0)
{
Tax = GIncome*0.13-23100;
}
else if (GIncome < 1780000.0)
{
Tax = GIncome*0.21-94300;
}
else if (GIncome < 3340000.0)
{
Tax = GIncome*0.3-254500;
}
else
Tax = GIncome*0.4 - 588500;
return Tax;
}

文件夹中含有：



输出结果: