98b736ecc3
One note: I didn't remove it, but Google's C++ coding standard forbids the use of using namespace std;
102 lines
4.4 KiB
Markdown
102 lines
4.4 KiB
Markdown
---
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title: C++
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---
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# Hello World! - Your First C++ Program
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## What is C++?
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* C++ is a general purpose programming language which has been used since the 1990's
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* It was designed by Bjarne Stroustrup under the name "C with classes".
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* It is a version of C that includes Object-Oriented elements, including classes and functions.
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* It is considered one of the biggest programming languages, as you can see in the following image:
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_source: Github_
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### Your First Program in C++
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```cpp
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#include <iostream>
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using namespace std;
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int main()
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{
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cout << "Hello World" << endl;
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return 0;
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}
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```
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#### The Output of this program will be:
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```
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Hello World!
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```
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Now, let's break down the code:
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#### Lines 1 and 2
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```cpp
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#include <iostream>
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using namespace std;
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```
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* The first line tells the computer to use the "iostream" header file for this specific program. A header file is a separate file with prewritten C++ code. There are many other header files which are required for a specific program to run properly. For example, math, vector, string, etc. Header files are generally represented by a ".h" extension, when including standard library header files you don't include the ".h" extension.
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* The `iostream` header contains the public interface for the input-output stream from the standard library. The "iostream" file contains code for allowing the computer to take input and generate an output, using the C++ language.
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* 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.
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#### Line 3 and 4
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```cpp
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int main()
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{
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```
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* 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)
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**NOTE : Every function starts with an opening curly brace "{" and ends with a closing curly brace "}".**
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* Line 4 indicates the start of the main() function.
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#### Lines 5, 6 & 7
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```cpp
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cout << "Hello World" << endl;
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return 0;
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}
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```
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* The word `cout` in C++ is used to stream data to standard output.
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* It is followed by `<<` , the _insertion operator_.
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* Whatever is in the double quotes `""` is printed. Certain special characters have a different syntax for print statements
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* Now to print any other kind of data, you have to add `<<`.
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***Challenge: Change Hello World to another sentence. What will be the output?***
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* `endl` is another symbol from the iostream library which means to **end this line and go to the next line during output** . - _cout stands for "console output"_
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* Finally, finish the statement with a semicolon `;`.
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**NOTE : Every statement except the main function definition and the #include directive needs to be ended by the semicolon. Without a ";", you may encounter a compiler error.**
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* `return 0;` safely terminates the current function i.e. 'main()' in this case and since no function follows after 'main()' the program is terminated.
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* 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 compiler error before program execution if you do not include the **}** .
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### The code should look something like this:
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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.
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_You have finished coding your first C++ program and have understood most of the code you have written/typed. CONGRATULATIONS!_
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**Good Luck to all of you and happy coding! :)**
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**Happy Coding ! :)**
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**Feel free to ask any questions on FreeCodeCamp's GitHub page or [FreeCodeCamp's Forum.](https://forum.freecodecamp.org/)**
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[Try it yourself ! :)](https://repl.it/L4k3)
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**You need software to write and execute C++ code, download from one of the links below:**
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[Codeblocks](http://www.codeblocks.org/downloads/26)
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[Xcode](https://developer.apple.com/xcode/)
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[Eclipse](http://www.eclipse.org/downloads/)
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