C++ Introduction

[yuethomas]

C++ is no different than other languages. Here's the hello world program in C++:

code:

#include <iostream.h> // this line imports the stuff needed for screen I/O void main() { // function declaration; main() is always executed when a program runs     cout << "hello world!\n"; // outputs a string to the standard output device, in this case, the screen (DOS prompt)     // backslash n is the newline symbol         cout << "Press enter to exit\n";     cin.ignore(1,'\n');     // these two lines prompt you to press "enter" key to terminate the program }

Keyboard input, basic math, string declaraction, string manipulation:

code:

#include <iostream.h> #include <string.h> // used for string manipulation void main () {     int a, b; // declaring variables of type integer     char c[50]; // declaring a string of length 49; alternatively, you can use the String class, but for brevity here we forego that     // make sure when you declare a character array, you allocate enough space for all your chars; going past 49, in this case, is ALLOWED, but unexpected results might happen     // note on strings: only at declaration can you give it a value, like     // char c[] = "hello world";     // after declaration, you cannot use a line like     // c = "hello world";     // you must use the strcpy(dest, source) function instead:     // strcpy(c,"hello world");     a=b=0; // setting the values of a and b to 0, called "initialis(z?)ation"     // initialisation is important in C++ because when memory spaces for variables are allocated, they are not set to 0 like in some other languages. If you attempt to output the values of uninitialised variables, whatever was in the memory when it was allocated will be outputted.     cout << "Please input a number:" << endl; // endl is the same as '\n'     cin << a; // inputting a number     cin.ignore(20,'\n'); // flushing the input stream, VERY IMPORTANT     cout << "Please input another number:" << endl;     cin << b;     cin.ignore(20,'\n');     cout << "Please input a string:"<<endl;     cin.getline(c,49,'\n'); // inputting a line; getline's syntax is     // getline(char* s, int l, char delim)     // s is the character array into which the string will be stored; disregard the * for now     // l is the maximum length of the character array (defined above)     // delim is the character with which we end the input (enter key in this case)     cout << "sum is " << a+b << endl;     cout << "difference is " << a-b << endl;     cout << "product is " << a*b << endl;     cout << "your original string is " << endl << c << endl << " and it has length " << strlen(c) << endl; // strlen returns the length of the string     cout << "press enter to exit" << endl;     cin.ignore(1,'\n'); }

For more information regarding strings (and C++ in general), visit http://www.cplusplus.com/.

Next tutorial: pointers, functions, advanced string functions