1. ITEC 320
C++ Examples

2. Hello World #include <iostream> using namespace std;
void main(int argc, char** argv) {
cout << “Hello World” << endl; }

3. Variables #include <iostream> #include <string>
using namespace std;
void main(int argc, char** argv) {
int x;
double y;
char z;
string a; }

4. Loops #include <iostream> #include <string>
using namespace std;
void main(int argc, char** argv) {
int i=0;
while(i<10)
cout << i << endl;
i++; }
for (int j=0; j<10; j++)
cout << j << endl;

5. Functions #include <iostream> #include <string>
using namespace std;
void print();
void main(int argc, char** argv) {
print(); }
void print()
cout << “Hello World” << endl;

6. Parameter passing #include <iostream> #include <string>
using namespace std;
void print(int& x, const int& y, const z);
void main(int argc, char** argv) {
int x=3;
int y=4;
int z=5;
print(x,y,z);
cout << x << y << z << endl; }
void print(int& x, const int& y, const z)
x=4; //X’s value in main is changed, Y/Z cannot be changed
//A copy of Z is made but y is not copied

7. Multiple files Compile with: g++ -o prog main.cpp print.cpp header.h
#ifndef __header_h_
#define __header_h_
void print();
#endif
Compile with:
g++ -o prog main.cpp print.cpp
Run:
prog or ./prog (windows / unix)
header.h
#include <iostream>
#include <string>
using namespace std;
#include “header.h”
void main(int argc, char** argv) {
print(); }
#include <iostream>
#include <string>
using namespace std;
#include “header.h”
void print() {
cout << “Hello World” << endl; }
main.cpp
print.cpp

8. Pointers #include <iostream> #include <string>
using namespace std;
void main(int argc, char** argv) {
int* p = NULL;
p = new int;
*p = 3;
cout << *p << endl; }

9. Arrays #include <iostream> #include <string>
using namespace std;
void main(int argc, char** argv) {
int first[10];
int* p = new int[10];
for (int i=0; i<10; i++)
first[i] = i;
p[i] = i; }
delete [] p;

10. Input #include <iostream> #include <string>
using namespace std;
void main(int argc, char** argv) {
int x;
string line;
cin >> x; //Read an integer, ignores preceding whitespace
getline(cin, line); //Reads until end of line
getline(cin, line, ‘\t’); //Reads up until the tab
cin.ignore(200,’\n’); // Ignore 200 chars or a new line
//whichever comes first }

11. Input / Looping #include <iostream> #include <string>
using namespace std;
void main(int argc, char** argv) {
int x;
cin >> x; //Read an integer, ignores preceding whitespace
while (!cin.eof() && !cin.fail())
if (x == 5) cout << “Magic number” << endl;
cin >> x; }
Prime the input before the loop
Otherwise it will repeat 1 more
Time than it should

12. File I/O #include <fstream> #include <string>
using namespace std;
void main(int argc, char** argv) {
ifstream i(“file.txt”);
ofstream o(“output.txt”);
int x;
i >> x;
o << x << endl;
i.close();
o.close(); }