106 lines
4.6 KiB
Markdown
106 lines
4.6 KiB
Markdown
---
|
|
title: C++
|
|
---
|
|
# Hello World! - Your First C++ Program
|
|
|
|
## What is C++?
|
|
|
|
* C++ is a general purpose programming language which has been used since the 1990's
|
|
* It was designed by Bjarne Stroustrup under the name "C with classes".
|
|
* It is a version of C that includes Object-Oriented elements, including classes and functions.
|
|
|
|
* It is considered one of the biggest programming languages, as you can see in the following image:
|
|
|
|
_source: Github_
|
|
|
|
### Your First Program in C++
|
|
|
|
```cpp
|
|
#include <iostream>
|
|
using namespace std;
|
|
int main()
|
|
{
|
|
cout << "Hello World" << endl;
|
|
return 0;
|
|
}
|
|
```
|
|
|
|
#### The Output of this program will simply be :
|
|
|
|
```
|
|
Hello World!
|
|
```
|
|
|
|
Now, let's break down the code:
|
|
|
|
|
|
#### Lines 1 and 2
|
|
|
|
```cpp
|
|
#include <iostream>
|
|
using namespace std;
|
|
```
|
|
|
|
* The first line tells the computer to use the "iostream" header file for this specific program . A header file is a seperate file with prewritten C++ code. There are many other header files which are requireed for a specific program to run properly. Some of them are : math , vector and string. Header files are generally represented by a ".h" extension (you don't need to add .h when including C++ standard library files)
|
|
* `iostream` stands for input-output stream . The "iostream" file contains code for allowing the computer to take input and generate an output, using the C++ language.
|
|
* The second line tells the computer to use the standard namespace which includes features of standard C++. You could write this program without this line, but you'd have to use `std::cout` instead of `cout` and `std::endl` instead of `endl` on line 4. It makes the code more readable and our lives as programmers easier.
|
|
|
|
#### Line 3 and 4
|
|
|
|
```cpp
|
|
int main()
|
|
{
|
|
```
|
|
|
|
* C++ starts execution of a program from the -main function- `int main()` . During execution , the computer starts running the code from every line from `{`(opening bracket) till `}`(closing bracket)
|
|
**NOTE : Every function starts with an opening curly brace "{" and ends with a closing curly brace "}".**
|
|
* Line 4 indicates the start of the main() function.
|
|
|
|
#### Lines 5, 6 & 7
|
|
|
|
```cpp
|
|
cout << "Hello World" << endl;
|
|
return 0;
|
|
}
|
|
```
|
|
|
|
* The word `cout` in C++ is used to output.
|
|
* It is followed by `<<` , the _insertion operator_ .
|
|
* Whatever is in the double quotes `""` is printed . Certain special characters have a different syntax for print statements
|
|
* Now to print any other kind of data , you have to add `<<` .
|
|
|
|
***Challenge: Try to change Hello World to any other sentence or word(s). What will be the output ?***
|
|
|
|
* `endl` is a reserved word when using the C++ language to **end this line and go to the next line during output** . - _cout stands for "console output"_
|
|
* Finally, finish the command with a semicolon `;`.
|
|
|
|
**NOTE : Every command except the main function definition and the #include directive needs to be ended by the semicolon. Without a ";" , you may encounter an error.**
|
|
|
|
* `return 0;` safely terminates the current function i.e. 'main()' in this case and since no function follows after 'main()' the program is terminated.
|
|
* Don't forget to tell the computer that this is end of the main() function. To do this , you add the closing curly brace "}". You will encounter an error before program execution if you do not include the **}** .
|
|
|
|
### The code should look something like this:
|
|
|
|
|
|
|
|
Programmers use a Hello World program (like this one) as a ritual on using a new programming language. It is a symbol of good luck.
|
|
_You have finished coding your first C++ program and have understood most of the code you have written/typed. CONGRATULATIONS!_
|
|
|
|
**Good Luck to all of you and happy coding! :)**
|
|
|
|
**Happy Coding ! :)**
|
|
|
|
**Feel free to ask any questions on FreeCodeCamp's GitHub page or [FreeCodeCamp's Forum.](https://forum.freecodecamp.org/)**
|
|
|
|
[Try it yourself ! :)](https://repl.it/L4k3)
|
|
|
|
**You may need some software to write and execute C++ code. I recommend using CodeBlocks. There's a download link below :**
|
|
|
|
Download Link : [Download Here](http://www.codeblocks.org/downloads/26)
|
|
|
|
* Click the link with the GNU/GCC compiler for windows. This will not require an additional installation
|
|
|
|
Other alternatives could be visual studio, using a compiler or an online IDE such as Cloud9 or repl.it
|
|
|
|
Link #2 for Mac : [Download for Mac #2 here](https://developer.apple.com/xcode/)
|