C++基本语法

C++练习

开始C++学习

// myfirst.cpp--displays a message

#include <iostream>                           // a PREPROCESSOR directive
int main()                                    // function header
{                                             // start of function body
    using namespace std;                      // make definitions visible
    cout << "Come up and C++ me some time.";  // message
    cout << endl;                             // start a new line
    cout << "You won't regret it!" << endl;   // more output
// If the output window closes before you can read it,
// add the following code:
    // cout << "Press any key to continue." <<endl;
	// cin.get();                                                   
    return 0;                                 // terminate main()
}                                             // end of function body

兔子个数

// carrots.cpp -- food processing program
// uses and displays a variable

#include <iostream>

int main()
{
    using namespace std;
    
    int carrots;            // declare an integer variable
    
    carrots = 25;            // assign a value to the variable
    cout << "I have ";
    cout << carrots;        // display the value of the variable
    cout << " carrots.";
    cout << endl;
    carrots = carrots - 1;  // modify the variable
    cout << "Crunch, crunch. Now I have " 
         << carrots << " carrots." << endl;
    // cin.get();
	return 0;
}

输入输出

// getinfo.cpp -- input and output
#include <iostream>

int main()
{
    using namespace std;
    
    int carrots;
    
    cout << "How many carrots do you have?" << endl;
    cin >> carrots;                // C++ input
    cout << "Here are two more. ";
    carrots = carrots + 2;
// the next line concatenates output
    cout << "Now you have " << carrots << " carrots." << endl;
	// cin.get();
	// cin.get();
    return 0;
}

数学函数

// sqrt.cpp -- using the sqrt() function

#include <iostream>
#include <cmath>    // or math.h

int main()
{
    using namespace std;
   
    double area;
    cout << "Enter the floor area, in square feet, of your home: ";
    cin >> area;
    // cin.get();
    double side;
    side = sqrt(area);
    cout << "That's the equivalent of a square " << side 
         << " feet to the side." << endl;
    cout << "How fascinating!" << endl;
	
	// cin.get();
    return 0;
}

没有返回值函数

// ourfunc.cpp -- defining your own function
#include <iostream>
void simon(int);    // function prototype for simon()

int main()
{
    using namespace std;
    simon(3);       // call the simon() function
    cout << "Pick an integer: ";
    int count;
    cin >> count;
    simon(count);   // call it again
    cout << "Done!" << endl;
	// cin.get();
    // cin.get();
    return 0;
}

void simon(int n)   // define the simon() function
{
    using namespace std;

    cout << "Simon says touch your toes " << n << " times." << endl;
}                   // void functions don't need return statements

有返回值函数

// convert.cpp -- converts stone to pounds
#include <iostream>
int stonetolb(int);     // function prototype
int main()
{
    using namespace std;
    int stone;
    cout << "Enter the weight in stone: ";
    cin >> stone;
    int pounds = stonetolb(stone);
    cout << stone << " stone = ";
    cout << pounds << " pounds." << endl;
	// cin.get();
    // cin.get();
    return 0;
}

int stonetolb(int sts)
{
     return 14 * sts;
}