Warning

# 1 - Standardní vstup a výstup

## Jmenné prostory, standardní vstup a výstup

#include  <stdio.h>    // C include, /usr/include, /usr/local/include

#include  <iostream>

namespace test
{
int a = 10;    // test::a
int b = 78;
}

using namespace std;
using namespace test;

int main()
{
printf ("ahoj C\n");

std::cout << "ahoj C++" << std::endl;

std::cout << "jedna" << " dva" << " tri" << std::endl;

std::cout << "10 + 30 = " << 10 + 30 << std::endl;

int a = 33;

std::cout << "a = " << a << ", test::a = " << test::a << std::endl;

cout << "a = " << a << ", test::a = " << test::a << endl;

cout << "b = " << b << endl;

/*
std::cout   std. vystup
std::cin    std. vstup
std::cerr   std. chybovy vystup
std::clog   std. logovaci vystup
*/

cout << "zadej cislo datoveho typu int: ";

cin >> b;

if (cin.good())
cout << "zadal jsi " << b << endl;
else
cout << "nauc se datove typy" << endl;

return 0;
}

## Formátování standardního výstupu

#include <iostream>
#include <iomanip>

using namespace std;

int main()
{
float pi = 3.14159265;
float pp = 65.876866;
float px = 768748.898;

cout << pi << endl << pp << endl << px << endl;

cout << setprecision(2);

cout << pi << endl << pp << endl << px << endl;

cout << fixed;

cout << "fixed: " << endl << pi << endl << pp << endl << px << endl;

cout << setprecision(5);

cout << pi << endl << pp << endl << px << endl;

cout << scientific;

cout << pi << endl << pp << endl << px << endl;

cout.unsetf (ios_base::floatfield);

cout << pi << endl << pp << endl << px << endl;

cout << setw(15) << pi << endl;

return 0;
}

## Reference

#include <iostream>

void f1(int *a)
{
*a = 31;
}

void f2(int &a)
{
a = 32;
}

int main()
{
int x = 10;

std::cout << "x = " << x << std::endl;

f1 (&x);

std::cout << "x = " << x << std::endl;

int &y = x;

f2 (x);

std::cout << "x = " << x << std::endl;

return 0;
}

## Jednoduchá práce se souborem.

#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
ifstream in ("04.cpp");
ofstream out ("04-copy.cpp");

if (in.good ())
{
cout << "soubor byl otevren" << endl;

string s;

while (getline (in, s))
{
cout << s << endl;
out << s << endl;
}
}

return 0;
}