第一個程序demo.cpp

編譯、運行

g++ -c demo.cpp
g++ -o demo.exe demo.o

解釋

最簡單的C++源文件

1 int main() {
2   return 0;
3}

使用cout 輸出一行字符串

  1 //this is sample for study
  2 #include <iostream>
  3
  4 int main() {
  5     std::cout << "This is a sample for study." << std::endl;
  6     return 0;
  7 } 

Screen Shot 2022-03-24 at 1.36.51 PM.png

使用命名空間

  1 //this is sample for study
  2 #include <iostream>
  3 
  4 using namespace std;
  5 int main() {
  6     cout << "This is a sample for study." << endl;
  7     return 0;
  8 }

使用變量

  1 //this is sample for study
  2 #include <iostream>
  3 
  4 using namespace std;
  5 int main() {
  7     int carrots;
  8 
  9     carrots = 25;
 10     cout << "I have " << carrots << " carrots." << endl;
 11 
 12     carrots = carrots - 1;
 13     cout << "Crunch, Crunch. Now I have "<< carrots << " carrots." << endl;
 14     return 0;
 15 }

從鍵盤輸入

  1 //this is sample for study
  2 #include <iostream>
  3 
  4 using namespace std;
  5 int main() {
  6     cout << "This is a sample for study." << endl;
  7     int carrots;
  8 
  9     carrots = 25;
 10     cout << "I have " << carrots << " carrots." << endl;
 13 
 14     cout << "Please input number:";
 15     cin >> carrots;
 16 
 17     cout << "Now ,I still hava " << carrots << " carrots." << endl;
 18 
 19     return 0;
 20 }