[C++] Chapter 2. Elementary Programming

• Reading Input from the keyboard
  • use cin

#include <iostream>
using namespace std;

int main()
{
	cout << "Width: ";
	int Width;
	cin >> Width;
	cout << "Height:";
	int Height;
	cin >> Height;
	int area = Width * Height;
	cout << " Area " << area << "\n";
}

• cin
• cout
• >>
• <<

Key Input to Buffer Stream of cin

• string, and char array

char	int	double	float	*
1byte	4byte	8byte	4bye	4byte

• sizeof / strlen
  • sizeof is byte size [sizeof is operator]
  • strlen is length [strlen is function]

-> string literal should have "\n"

 

• Password check [cin]

#include <iostream>
using namespace std;

int main()
{
	cout << "name : ";
	char name[20];
	cin >> name;
	cout << "your name is : " << name << endl;

	char pwd[100];
	cout << "enter your password: " << endl;
	while (true)
	{
		cout << "password : ";
		cin >> pwd;
		if (strcmp(pwd, "C++") == 0)
		{
			cout << "Password is correct program exit" << endl;

			break;
		}
		else
		{
			cout << "wrong password" << endl;

		}

	}

	return 0;
}

-> string literal comparsion check fucntion : strcmp [문자열 비교함수 : strcmp ( A, B )]

• Line by Line input
  • not cin is no space input
  • getline
• getline funciton
  • Reading a string with space in it [Read a line by line]
  • cin.getline(char buf[], int size, char delimitChar)
    • when encountering delimitChar, input stops

#include <iostream>
using namespace std;

int main()
{
	cout << "name : ";
	char name[20];
	cin.getline(name, 20,'\n');
	cout << "your name is : " << name << endl;
	

	char pwd[100];
	cout << "enter your password: " << endl;
	while (true)
	{
		cout << "password : ";
		cin.getline(pwd, 100);

		if (strcmp(pwd, "C ++") == 0)
		{
			cout << "Password is correct program exit" << endl;

			break;
		}
		else if(strcmp(pwd, "\0" )==0) // enter key 
		{
			cout << "program exit" << endl;
			break;
		}
		else
		{
			cout << "wrong password" << endl;

		}

	}

	return 0;
}

---

• Named Constants

const datatype CONSTANTNAME = VALUE;

const double PI = 3.141592;
const int SIZE = 3;